International CAWSES-II Symposium
EUVI 171, 11-Apr-2013 02:14:00
1000

Y (arcsecs)

500
0
-500
-1000
-1000 -5000500
X (arcsecs)

EUVI 171, 11-Apr-2013 02:14:00

400

300

300

200

200

100

AR

0

100

EUVI 171, 11-Apr-2013 02:14:00

400

FP1
LT

0

-100

-100

-200
-1000 -900 -800 -700 -600 -500 -400
X (arcsecs)-200-1000 -900 -800 -700 -600 -500 -400
X (arcsecs)

FP2

300
Y (arcsecs)

400

Y (arcsecs)

Y (arcsecs)

EUVI 304, 11-Apr-2013 02:46:15

1000

200
100
0
-100
-200
-1000 -900 -800 -700 -600 -500 -400
X (arcsecs)

Editorial Board (Mar. 2016)
Editor-in-Chief
Yasuo Ogawa, Tokyo Institute of Technology, Japan

Editorial Board
Yosuke Aoki, University of Tokyo, Japan
Nanan Balan, University of Sheffield, United
Kingdom
Stephen Bannister, GNS Science, New Zealand
Benjamin Fong Chao, Academia Sinica, Taiwan
Shanaka de Silva, Oregon State University, U.S.A.
Koji Fukuma, Doshisha University, Japan
Nobuo Geshi, Geological Survey of Japan, AIST,Japan
Lin-Ni Hau, National Central University, Taiwan
Hauke Hussmann, German Aerospace Center,
Germany
Hiroo Kanamori, California Institute ofTechnology, U.S.A.
Attila Komjathy, National Aeronautics and Space
Administration, U.S.A.
Alexey Kuvshinov, Swiss Federal Institute ofTechnology Zurich, Switzerland
Takuto Maeda, University of Tokyo, Japan
Koji Matsumoto, National Astronomical
Observatory, Japan

Mitsuhiro Nakagawa, Hokkaido University, Japan
Junichi Nakajima, Tokyo Institute of Technology,
Japan
Yasuhiro Nariyuki, University of Toyama, Japan
Nozomu Nishitani, Nagoya University, Japan
Azusa Nishizawa, Japan Coast Guard, Japan
Keiji Ohtsuki, Kobe University, Japan
Taku Ozawa, National Research Institute for Earth
Science and Disaster Prevention, Japan
Takeshi Sakanoi, Tohoku University, Japan
Martha K. Savage, Victoria University of
Wellington, New Zealand
Benoit Taisne, Nanyang Technological University,
Singapore
Hiroshi Takenaka, Okayama University, Japan
Hiroaki Toh, Kyoto University, Japan
Yih-Min Wu, National Taiwan University, Taiwan
Zhongliang Wu, China Earthquake Administration,
China
Toshitsugu Yamazaki, University of Tokyo, Japan
Akimasa Yoshikawa, Kyushu University, Japan

Journal Scope
Earth, Planets and Space (EPS) is the official journal of the Society of Geomagnetism and Earth, Planetary
and Space Sciences, The Seismological Society of Japan, The Volcanological Society of Japan, The
Geodetic Society of Japan, and The Japanese Society for Planetary Sciences.
EPS is a peer-reviewed, open-access journal published under SpringerOpen. It is an international journal
covering scientific articles in the entire field of earth and planetary sciences, particularly geomagnetism,aeronomy, space science, seismology, volcanology, geodesy, and planetary science. EPS also welcomesarticles in new and interdisciplinary subjects, and technical reports on instrumentation and software.
The journal was launched in 1998 and has since published over 2700 articles. All of them are available forfree on SpringerLink:
http://link.springer.com/journal/40623
More information about the journal, its article collections, and the submission process is available on thejournal homepage:
http://www.earth-planets-space.com/
Submit your next research article to Earth, Planets and Space via:
https://www.editorialmanager.com/epsp
Yours sincerely,
Prof. Yasuo Ogawa
Editor-in-Chief, Earth, Planets and Space
editor-in-chief@earth-planets-space.org

Earth, Planets and Space
Yamamoto et al. Earth, Planets and Space (2016) 68:26
DOI 10.1186/s40623-016-0392-6

PREFACEOpen AccessSpecial issue “International CAWSES-II
Symposium”
Mamoru Yamamoto1*, Kazuo Shiokawa2, Takuji Nakamura3 and Nat Gopalswamy4
Abstract
This special issue gathered papers from the International CAWSES-II Symposium (November 18–22, 2013 at Nagoya
University, Japan). Climate and Weather of the Sun-Earth System II (CAWSES-II) is an international scientific program
sponsored by Scientific Committee on Solar-Terrestrial Physics (SCOSTEP) that continued from 2009 to 2013. The
program was established with the aim of significantly enhancing our understanding of the space environment andits impacts on life and society. The International CAWSES-II Symposium was successful with 388 presentations; andfrom that, 38 papers were published in this special issue. In this preface, we briefly discuss the contents of thespecial issue as well as the CAWSES-II review papers published in Progress in Earth and Planetary Science (PEPS) in
2014–2015.
Keywords: Sun-Earth system, Solar-terrestrial physics, International program, CAWSES-II, SCOSTEPIntroduction
Climate and Weather of the Sun-Earth System II(CAWSES-II), an international program sponsored by Scientific Committee on Solar-Terrestrial Physics (SCOSTEP),
was established with an aim of significantly enhancing ourunderstanding of the space environment and its impacts onlife and society. This program was conducted from 2009 to2013 to follow the CAWSES program that continued from2004 to 2008. In contrast to a very low solar activity during
the CAWSES period, CAWSES-II was conducted during
the earlier stage of the recent solar cycle 24. The project
was then subtitled “Towards solar maximum.” During
November 18–22, 2013, the International CAWSES-II
Symposium was held at Nagoya University in Japan inorder to provide an excellent opportunity to discuss thescientific accomplishments of CAWSES-II near the end ofits 5-year period and look forward to SCOSTEP’s future
programs. The symposium was very successful with 320
participants from 33 countries/areas, and 388 papers were
presented. This special issue, published in 2014–2015,
gathered 38 excellent papers from this symposium. In
addition to this special issue, reviews of all aspects of
CAWSES-II were published in Progress in Earth andPlanetary Science (PEPS) during the same period. These
are two important activities to summarize the scientificprogram of CAWSES-II. In this preface, we will highlightthe papers from our special issue together with the reviews in PEPS. We also note that these publications wererecently compiled in a book entitled “Selected publications
from the SCOSTEP/CAWSES II project” (ISBN 978-4904090-15-2 C3044).

Contents of the special issue
CAWSES-II program

The overall review of CAWSES-II was given in Tsudaet al. (2015). It stated that “The CAWSES program wasaimed at improving the understanding of the coupledsolar-terrestrial system, with special emphasis placed on
the short-term (weather) and long-term (climate) variability of solar activities and their effects on and responses ofgeospace and Earth’s environment” with “time-scale ranging from minutes to millennia.” CAWSES-II pursued thisgoal by establishing four task groups, which were identified by the key questions of research fields as shown
below.
– Task group 1 (TG1): What are the solar influenceson climate?
– Task group 2 (TG2): How will geospace respond toan altered climate?

* Correspondence: yamamoto@rish.kyoto-u.ac.jp
1
Research Institute for Sustainable Humanosphere (RISH), Kyoto University,
Gokasho, Uji, Kyoto 611-0011, Japan
Full list of author information is available at the end of the article© 2016 Yamamoto et al. Open Access This article is distributed under the terms of the Creative Commons Attribution 4.0
International License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, andreproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link to
the Creative Commons license, and indicate if changes were made.

1

International CAWSES-II Symposium
Yamamoto et al. Earth, Planets and Space (2016) 68:26

Page 2 of 8

potential gradient oscillations with amplitudes up to
300 V/m. Muraki et al. (2015) studied regional climate
patterns over 2000 years as estimated from the annual
tree rings of Yaku cedar trees from Yakushima, Japan.
They discovered an 11-year periodicity in the meteorological daylight-hour data in the month of June from1938 to 2013 and a 24-year periodicity in July. The
growth rate of the tree rings may be affected by thevariation in the daylight hours.

– Task group 3 (TG3): How does short-term solar
variability affect the geospace environment?
– Task group 4 (TG4): What is the geospace response
to variable inputs from the lower atmosphere?
In addition to these task groups, CAWSES-II put significant effort into “capacity building” and “E-scienceand Informatics,” both of which are important for future
development of the research field. In the following, wecategorize papers from our special issue by task groups
and E-science and also refer to the related review papers
in PEPS.

Task group 2

The key question of task group 2 (TG2) was “How willgeospace respond to an altered climate?” Laštovička et al.
(2014) reviewed the research activities of the task group. It
was stated that long-term trends in the mesosphere,
thermosphere, and ionosphere are areas of research of increasing importance, both because they are sensitive indicators of climatic change and because they affect satellitebased technologies that are increasingly important tomodern life. During the CAWSES-II period, significant
progress was achieved in several areas, such as understanding and quantifying the role of stratospheric ozone
changes in trends in the upper atmosphere, reachingreasonable agreement between observed and simulated
trends in mesospheric temperatures and polar mesosphericclouds, and understanding why the thermospheric density
trends are much stronger under solar cycle minimum
conditions (Laštovička et al. 2014).
In our special issue, six papers are categorized in TG2.
Pertsev et al. (2014) studied long-term ground observations of the noctilucent clouds and found that the occurrence of the noctilucent clouds was correlated to thehumidity of the mesosphere that corresponded to thesaturated or supersaturated water vapor. However, there
was no statistically significant long-term trend in either
the occurrence or brightness of the noctilucent cloud
when a weather correction was applied. Gan et al. (2014)
studied the climatology of the diurnal tides from the extended Canadian Middle Atmosphere Model (eCMAM)
run in a nudged mode using reanalysis data of the groundto 1 hPa for the period of January 1979 to June 2010 andthe satellite data from Sounding of the Atmosphere using
Broadband Emission Radiometry (SABER) in the period
from January 2002 to December 2013. The diurnal tidal
spectra and their relative strengths compared very well
between eCMAM30 and SABER. A variation with aperiod of 25 to 26 months was found, which indicatesthe modulation of the diurnal tides by the stratosphericquasi-biennial oscillation (QBO). Elias (2014) studied
the foF2 long-term trend that was linked to the anthropogenic effects. It was found that 90 % of the foF2
variation is owing to the solar variability. It is recommended
that the F10.7 index should be used for the filtering process,as it is better proxy to the solar EUV compared with the

Task group 1

Task group 1 (TG1) of CAWSES-II tackled the key
question “What are the solar influences on climate?”
Seppälä et al. (2014) reviewed the research activities of
TG1. They showed different aspects of solar forcing fromsolar irradiance and demonstrated proposed mechanisms
by which solar variation could influence the Earth’s climate. Major questions in TG1 were as follows: What is
the importance of spectral variations to solar influenceson climate? What is the effect of energetic particle forcing
on the whole atmosphere and what are the implications
for climate? How well do models reproduce and predict
solar irradiance and energetic particle influences on theatmosphere and climate? Through CAWSES-II, solar
influence on climate is now accepted as an important
contribution to climate variability particularly on regional
scales. Also, ionization rates and chemical changes by theenergetic particle precipitation are now better understood.
For climate models which include effect of the solar cycle,
however, more efforts are needed (Seppälä et al. 2014).
In our special issue, four papers were published for
TG1. Elias et al. (2014) studied the effect of solar cycle
23 in critical frequency (foF2) trend estimation, in which
they used ionosonde and model data to estimate thelong-term decreasing trend of foF2. The result of thestudy was consistent with those expected from the greenhouse gas effect. Kozai et al. (2014) studied the spatial
density gradient of galactic cosmic rays and their solar
cycle variation observed with the Global Muon Detector
Network (GMDN). The authors compared the threedimensional (3D) anisotropy of approximately 60 GV
galactic cosmic rays (GCRs) from the data observedwith the GMDN with conventional analysis with a single muon detector at Nagoya in Japan. They found thatboth results were fairly consistent as far as the yearlymean value was concerned. Smirnov (2014) studied thereaction of the electric and the meteorological states of
the near-ground atmosphere during a geomagnetic storm
on April 5, 2010. It was found that air electro-conductivity
began to decrease 4 hours before the storm, which lasted
for 20 hours. The storm’s sudden commencement caused2

Earth, Planets and Space
Yamamoto et al. Earth, Planets and Space (2016) 68:26

Page 3 of 8

events also did not have GLEs, mainly because of thelower CME speed. Sasai et al. (2014) reported a new project of observing solar neutrons at Mt. Sierra Negra in
Mexico. The project is named SciBar Cosmic Ray Telescope (SciCRT) and aims to study the mechanism of ion
acceleration on the surface of the Sun and to monitor the
anisotropy of galactic cosmic-ray muons. The system wasinstalled in April 2013, and its detection performance wasreported. Iwai et al. (2014) studied the coronal magnetic
field and the plasma beta (plasma pressure/magnetic pressure). They utilized radio free-free emission data from theNobeyama Radioheliograph (NoRH) and multiple lineof-sight extreme ultraviolet (EUV) light observations
from the Atmospheric Imaging Assembly (AIA) onboard the Solar Dynamics Observatory (SDO) and the
EUV imager onboard the Solar Terrestrial Relations
Observatory (STEREO) and achieved more accurate estimations of the coronal parameters than have ever previously been derived. Lopez and Matsubara (2015) studied
solar neutrons at Mt. Chacaltaya associated with M- andX-class flares during the rising period of solar cycle 24 inorder to better understand the acceleration mechanism ofhigh-energy particles that are driven by solar flares. They
found that no statistically significant solar neutron signals
were found from the sample, which consisted of 28
M-class and 3 X-class flares. Also, an estimation of theupper limit for solar neutrons to arrive at Mt. Chacaltaya
was suggested as 1.07 × 1027/MeV/sr on the Sun.
Prikryl et al. (2014) studied high-latitude Global Positioning System (GPS) phase scintillation and cycle slips
during high-speed solar wind streams and CMEs by superposed epoch (SPE) analysis. The occurrence of scintillation peaked on days with high-speed solar windstreams (HSS) or with CME impacts at the Earth’s magnetosphere. They tapered off a few days later, which issimilar to the day-to-day variability of geomagnetic activity and riometer absorption at high latitudes. The SPE
analysis results were used to obtain cumulative probability distribution functions for the phase scintillation occurrence that could be employed in probabilistic forecasts ofphase scintillation at high latitudes. Kumar and Kumar(2014) studied the effects of the solar flares and the geomagnetic storms during December 2006 to 2008 by theinvestigation of very low frequency (VLF) signals received
at Suva in Fiji. The enhancement in the amplitude andphase of VLF signals by solar flares was due to the increase in the D-region electron density by the solar flareproduced extra ionization. Uwamahoro and Habarulema(2014) studied empirical modeling of the storm time geomagnetic indices. They used a neural network to predict
Kp index and the local K index from geomagnetic fielddata from Hermanus, South Africa, with inputs of thesolar wind particle density; the solar wind velocity; theinterplanetary magnetic field (IMF); the total average field,

Zurich relative sunspot number (Rz). Gordiyenko et al.
(2014) studied long-term trends in the foF2 as observed at
Alma-Ata ionosonde station from 1957 to 2012. The F10.7
and Ap indexes were used to remove shorter variability ofthe parameter. Results of the analysis showed a long-term
trend of −0.0075 MHz/year for the annual mean foF2, which
was consistent with the results by Elias (2014). Bychkov
et al. (2014) investigated the correlation of 532-nm lidar
returns at Kamchatka with the night ionospheric F2 layer
and found the role of excited nitrogen ions in the formationof lidar signals. Shinbori et al. (2014) investigated characteristics of the long-term variation in the amplitude of solar
quiet (Sq) geomagnetic field daily variation by using 1-h geomagnetic field data obtained from 69 geomagnetic observation stations within the period of 1947 to 2013. They
showed clear dependence of the Sq amplitude on the solar
activity. The long-term trend of the Sq amplitude was generally negative over a wide region. The authors showed thatthe relationship between the magnetic field intensity
and residual Sq amplitude was an anticorrelation forabout 71 % of the geomagnetic stations and impliedthat there was a movement of the equatorial electrojet
due to secular variation of the ambient magnetic field.
Task group 3

The key question of task group 3 (TG3) was “How does
short-term solar variability affect the geospace environment?” Gopalswamy et al. (2015) reviewed the scientificachievements of TG3 during CAWSES-II. In particular,
after a deep minimum following cycle 23, the Sun
climbed to a very weak maximum in terms of the sunspot number in cycle 24, so that many of the results referred to this weak activity in comparison with cycle 23.
There were many studies of the short-term variability,
manifested as solar eruptions from closed-field regions
and high-speed streams from coronal holes, which have
immediate consequence to the Earth and the geospace.
In addition, there was a progress of studies of extreme
space weather events prompted by the July 23, 2012superstorm event (Gopalswamy et al. 2015).
In our special issue, 12 papers were categorized in TG3.
Gopalswamy et al. (2014) reported on all major solar eruptions that occurred on the front side of the Sun during therise to the peak phase of cycle 24 in order to understandthe key factors affecting the occurrence of large solar energetic particle (SEP) events and ground level enhancement(GLE) events. The authors examined the reason for thepaucity of GLE events during the period. Most of theeruptions with high coronal mass ejection (CME) speed(>2000 km/s) had poor connection to the Earth, so thehighest-energy particles may not have reached the Eartheven though they may have been accelerated. There werea few eruptions with high CME speed and good connection, yet they lacked GLEs. Many well-connected SEP

3

International CAWSES-II Symposium
Yamamoto et al. Earth, Planets and Space (2016) 68:26

Page 4 of 8

frequency and time. It was suggested that the frequencydependent events, which usually last several tens of minutes, might be the consequence of the broadening of theray path that the waves follow from their generation region to the ground.

Bt; and the IMF Bz component. The model gave good predictability of the Hermanus storm time K index with acorrelation coefficient of 0.8. Jun et al. (2014) studied Pc1
pearl structures observed at ground stations in Russia,
Japan, and Canada. They selected two Pc1 pulsations. In
case 1, Pc1 pearl structures were slightly different duringsome time intervals at different stations, and theirpolarization angles varied depending on the frequencies.
In case 2, Pc1 pearl structures were similar at different
stations, and their polarization angle was independentof frequency. Case 1 was explained by the beating of
Pc1 pearl structures in the ionosphere, while case 2 was
explained by magnetospheric effects. Kondoh and Shimizu(2014) investigated tailward flow in the near-Earth plasma
sheet associated with a rebound of the earthward bursty
bulk flow (BBF) by using 3D magnetohydrodynamic simulations of magnetic reconnection in the magnetotail on
the basis of the spontaneous fast reconnection model. It
was found that, as a result of the rebound of the earthward
flow, the accumulation of the plasma density and theplasma pressure was observed at any position in theplasma sheet during the interval between the BBF andthe reverse flow. Mandrikova et al. (2014) studied methodsof analysis of geomagnetic field variations and cosmic ray
data. They proposed a wavelet-based method of describing
variations in the Earth’s magnetic field, such as the horizontal component of the geomagnetic field, in addition tomethods for evaluating changes in the energy characteristics of the field and for isolating the periods of increased
geomagnetic activity. The analysis showed that in periodsof increased geomagnetic activity, the developed methods
allowed the recording of the onset of geomagnetic disturbances and quantitative estimates of the power of the geomagnetic field disturbance. Cherniak et al. (2014) studied
the influence of ionospheric irregularities on Global
Navigation Satellite System (GNSS) applications. They
used data from the permanent GNSS network to develop an empirical model of the ionospheric irregularities over the northern hemisphere. The rate of total
electron content (TEC) index (ROTI) maps was used
for the estimation of the overall fluctuation activity andthe auroral oval evolution. They also showed the correlations between the Kp index and parameters that characterized the activity of the ionosphere irregularities
from 2010 to 2013. Martinez-Calderon et al. (2015)
conducted polarization analysis of VLF/extremely low
frequency (ELF) waves at subauroral latitudes based on
the VLF Campaign observation with the High-resolution
Aurora Imaging Network (VLF-CHAIN) from February
17 to 25, 2012. Among the naturally occurring VLF and
ELF radiations, chorus wave emissions are one of the mostintense phenomena. The authors observed several types of
VLF/ELF emissions, including chorus, and found that thepolarization angle of several emissions depended on both

Task group 4

Task group 4 (TG4) of CAWSES-II aimed to answer the
key question: “What is the geospace response to variable
inputs from the lower atmosphere?” Oberheide et al.
(2015) reviewed the achievements of TG4 during
CAWSES-II. They identified the progress of the researchas the advent of new satellite missions, ground-based instrumentation networks, and the development of wholeatmosphere models over the past decade. This resulted
in a paradigm shift in the understanding of the variabilityof geospace, that is, the region of the atmosphere between
the stratosphere and several thousand kilometers above
ground where atmosphere-ionosphere-magnetosphereinteractions occur. The progress made during the
CAWSES-II time period is reviewed emphasizing therole of gravity waves, planetary waves and tides, andtheir ionospheric impacts (Oberheide et al. 2015).
In this category, there are 16 papers in our special issue.
Fytterer et al. (2014) studied the global distribution of the
migrating terdiurnal tide in the sporadic E occurrence frequencies based on a GPS radio occultation experimentwith FORMOSAT-3/COSMIC satellites. Using 6-year averages from December 2006 to November 2012, a global
distribution of the terdiurnal oscillation in the occurrence
frequency of sporadic E was obtained from 60° S to 60° N.
The authors found two peaks above 100 km during thesolstice with one maximum at low and midlatitudes ineach hemisphere. Comparisons with the neutral wind behavior from simulation and satellite observations showed
good agreement for data above 100 km. Gavrilov andKshevetskii (2014) studied the 3D numerical simulation of
nonlinear acoustic-gravity wave (AGW) propagation fromthe troposphere to the thermosphere. Horizontally moving periodical structures of vertical velocity on the Earth’s
surface were used as AGW sources in the model. The
numerical simulation covered altitudes from the ground
up to 500 km. It was found that, in a few minutes, atmospheric waves can propagate to high altitudes above
100 km after activation of the surface wave force. AGWs
may transport amplitude modulation of atmospheric wave
sources in horizontal directions up to very high levels.
Laskar et al. (2014) studied vertical coupling of atmospheres depending on the strength of sudden stratosphericwarming (SSW) and solar activity. The equatorial electrojet (EEJ) strength and the TEC data from low latitudes
over Indian longitudes during the mid-winter season in
the years 2005 to 2013 were used. The authors concluded
that the vertical coupling of atmospheres in terms of the4Earth, Planets and Space
Yamamoto et al. Earth, Planets and Space (2016) 68:26

Page 5 of 8

measurements. The results indicated that good correlations existed only in the south American sector and tosome extent in the African sector, which implied thatthe gravity wave induced in the ITCZ cannot be thesole seeding agent for the Rayleigh-Taylor (RT) instability in the global irregularity occurrences every season.
The authors suspected that the post-sunset ionosphericelectrodynamic perturbations could be the prevailingseeds for the year-long RT instability globally. Narayanan
et al. (2014) investigated ionosonde observations made at
5-min intervals at the Indian dip equatorial station fromMarch 2008 to February 2009 and studied the interlink
between equatorial spread F (ESF) and satellite traces(STs), which are assumed to represent tilts in the bottomside isoelectron density surfaces probably caused by largescale wave-like structures (LSWS). They found that nearly
half of the ESF events were preceded by ST. Following thefirst occurrence of ST, the ESF onset was delayed by about
30 min on the average, suggesting that ST may be used asa precursor of ESF. Pre-reversal enhancement (PRE) of
upward plasma drift was found to be insignificant during
the period of study. Abdu et al. (2015) investigated therole of eastward and upward propagating fast (FK) and ultrafast Kelvin (UFK) waves in the day-to-day variability ofequatorial evening PRE and post-sunset generation of
ESF. The vertical drift oscillations were found to cause significant modulation in ESF development. The overall results highlighted the role of FK/UFK waves in the day-today variability of ESF in its occurrence season. Shpynev
et al. (2015) investigated the impact of dynamic processes
in the neutral atmosphere on the high-midlatitude ionosphere during two SSW events. In the case from January
2009, the authors found a negative effect in foF2 and apositive effect in F2 layer maximum (hmF2) above theborder of a stratospheric cyclone and an anticyclone withnorthward flow direction. In January 2013, they found apositive effect in foF2 up to approximately 2.5 MHz and anegative effect in hmF2 at approximately 10 km above thecenter of the stratospheric cyclone. It was concluded thatthese effects were caused by the upward transport ofmolecular gas to the lower thermosphere for the firstcase and a pulldown forcing of molecular species above
the low-pressure zone inside the cyclone for the secondcase. Oinats et al. (2015) conducted a statistical study of
medium-scale traveling ionospheric disturbances (MSTID)
using SuperDARN Hokkaido ground backscatter data for2011. They found four peaks with a distinct diurnal andseasonal dependence in the MSTID azimuth occurrence
rate distributions. Shiokawa et al. (2015) reported the firstobservation of the disappearance of ESF over geomagnetically conjugate points with data from airglow imagers at
Darwin, Australia, and Sata, Japan, on August 8, 2002. It isreported that ESF observed in 630-nm airglow images
from 1530 (0030 LT) to 1800 UT (0300 LT) disappeared

strength of the spectral amplitude was found to be
dependent on the strength of SSW, the solar activity, andthe interaction between tides and planetary waves. Ren
et al. (2014) studied the influence of DE3 tides on theequinoctial asymmetry of the zonal mean ionosphericelectron density by using the Global Coupled IonosphereThermosphere-Electrodynamics Model, Institute of Geology
and Geophysics, Chinese Academy of Sciences (GCITEMIGGCAS). The authors showed that the results varied withlatitude, altitude, and solar activity level. Compared with thedensity driven by the September DE3 tide, the March DE3tide mainly decreased the lower ionospheric zonal meanelectron density and mainly increased the electron density athigher ionosphere. It is also reported that DE3 tides drive anequatorial ionization anomaly (EIA) structure at higher
ionosphere in the relative difference of zonal mean electron
density. This suggests that DE3 tides affect the longitudinalmean equatorial vertical E × B plasma drifts. Truskowski
et al. (2014) and Forbes et al. (2014) conducted a two-partstudy of thermosphere tides. Truskowski et al. (2014), inpart 1, investigated TIMED/SABER temperature measurements at 110 km and between ±50° latitude from 2002
through 2010 and revealed the tidal spectrum entering theionosphere-thermosphere system. The tidal spectrum obtained by the analysis was especially relevant to the dynamo
generation of electric fields, which then imposed the tidal
variability on the overlying F-region ionosphere. Forbes
et al. (2014), as part two of the study, presented multi-year
and 72-day mean seasonal-latitudinal tidal structures in exospheric temperature derived from the joint analysis of
CHAMP and GRACE accelerometer measurements. With
the aid of theory and a simulation model, the authors
presented data consistent with those observed at
110 km and presented in part 1. The aggregate sum of
all of the tidal components was shown to impose considerable longitude and month-to-month variability on
the exosphere temperature tidal spectrum. Hamid et al.
(2014) studied the relationship between the EEJ andglobal Sq currents at the dip equator region. They examined the EEJ-Sq relationship by using observations at
six stations in the south American, Indian, and southeast Asian sectors. A weak positive correlation between
the EEJ and Sq was obtained in the southeast Asian
sector, while weak negative correlations were obtainedin the south American and Indian sectors. These results
demonstrated that the southeast Asian sector is different from the Indian and south American sectors, which
was indicative of a unique physical processes related tothe electro-dynamo. Su et al. (2014) studied the seedingmechanism of ionospheric irregularity occurrences bycorrelating the global monthly/latitudinal distributionsof irregularity occurrences and the deep atmospheric
convection in the intertropical convergence zone (ITCZ)
indicated by the outgoing longwave radiation (OLR)

5

International CAWSES-II Symposium
Yamamoto et al. Earth, Planets and Space (2016) 68:26

Page 6 of 8

and a geographical display tool that uses Google Earth(KML file). In addition, the study by Shinbori et al.
(2014) was based on the IUGONET data and its data
analysis tool.

toward the equator at 1800 to 1900 UT (0300 to 0400 LT)
in the field of view. At Darwin, the F-layer virtual heightsuddenly increased, but it did not increase over the conjugate point at Yamagawa. The authors explained this eventby indicating that a polarized electric field associated withthis equatorward neutral wind drove a plasma drift acrossthe magnetic field line to cause the observed ESF disappearance. Abadi et al. (2015) investigated the effects of
the F region bottomside altitude (h’F), the maximum
upward E × B drift velocity, the duration of PRE, andthe integral of upward E × B drifts on the latitudinal extension of ESF in the southeast Asian sector by using
GPS receivers and ionosondes. They found that ESF
reached magnetic latitudes of 10°–20° in the following
conditions: (1) the peak value of h’F was greater than
250–450 km, (2) the maximum upward E × B drift was
greater than 10–70 m/s, and (3) the integral of upward
E × B drift was greater than 50–250 m/s.

Summary

The main functions of CAWSES-II were to help coordinate international activities in observations, modeling,
and applications crucial to achieving an understandingof the Sun-Earth system, to involve scientists in bothdeveloped and developing countries, and to provide
educational opportunities for students of all levels. The
International CAWSES-II Symposium in November 2013
gathered a large number of scientists from around theworld, and 388 papers were presented. This special issue
from the symposium is composed of 38 excellent papers from the symposium. Also, the achievements of
CAWSES-II were reviewed by the leaders of the fourtask groups and the E-science component of the project.
The overall success of CAWSES-II can be summarized asfollows:

E-science

Fox and Kozyra (2015) reviewed E-science and Informatics in CAWSES-II. The authors stated that the effort
had the goal of promoting an international virtual institute and several virtual observatories in order to advancesystem-level science investigations aligned with the four
CAWSES-II task groups. They examined what was
adopted for CAWSES-II and highlighted the successes
and challenges of the effort. They evaluated that the degree of effectiveness of E-science and Informatics efforts
varied widely across the CAWSES-II activities, but generally was limited. However, there was a subcommunitythat embraced newer forms of collaboration, such as
MediaWiki, in what appeared to be a very effective way.
They encouraged future international science programs toconsider the benefits and resource costs of enhancing thevirtual participation opportunities (Fox and Kozyra 2015).
In our special issue, there are two technical reports
published in relation to this category. Abe et al. (2014)
reported on Progress of the Inter-university Upper Atmosphere Global Observation NETwork (IUGONET)
project, which aimed to establish a metadata database ofvarious ground-based observation data covering a wide
region from the Sun to the Earth. For archiving purposes, the metadata database system for cross-searchingvarious data distributed across many institutions was developed based on the existing repository software called
DSpace as the core component and the Space Physics
Archive Search and Extract (SPASE) data model as themetadata format. Yatagai et al. (2015) gave an overview
of the capacity-building activities and science-enabling
services related to IUGONET. They regularly facilitatedtraining seminars for Japanese students and also in developing countries. IUGONET prepared various tools
for users that included the IUGONET data analysis tool

– Study of the geospace environment was one of mostimportant issues in CAWSES-II. The most intense
variability of the geospace originates from the Sun,but through studies in CAWSES-II, it is now
understood that similarly important influences comefrom the lower atmosphere through wave dynamics.
This suggests the necessity for a deeper understandingof the Sun-Earth coupling processes.
– The understanding of a variety of solar variabilities
was greatly enhanced during CAWSES-II. The solar
minimum between cycles 23 and 24 was the weakest
among recent solar cycles and became an important
study area in the field. We also obtained a deeper
understanding on the mechanisms of how short-term
variability of the Sun affects the Earth. For example,
reliable computer simulations are becoming available
for space-weather nowcasting/forecasting.
– For studying the long-term variability of the geospace,a careful investigation of the relationship with the
Earth’s climate is necessary. Great effort was expended
in this area during the period of CAWSES-II. The
study of the Earth’s climate change in response to thesolar variability is also rapidly progressing. Better
understanding of the long-term Sun-Earth couplingis an important achievement of CAWSES-II.
– E-science and Informatics was a new element in
CAWSES-II. This movement is still under progress
during the program period, partly because theunderstanding and computer/network skill of theparticipating researchers did not reach the level
the leaders had expected. However, there weresome achievements regarding the virtual poster

6

Earth, Planets and Space
Yamamoto et al. Earth, Planets and Space (2016) 68:26

Page 7 of 8

activities and database developments shown in thereview paper and the special issue papers.
– In addition, CAWSES-II paid much attention to thecapacity building for young scientists and researchers
from Asian and African countries. This movement
was not largely reported in the reviews, but we canfind its success in the fact that many young scientists
have written papers in the special issue, and some
papers are from Asian and African countries.

Bychkov VV, Nepomnyashchiy YА, Perezhogin AS, Shevtsov BM (2014) Lidar
returns from the upper atmosphere of Kamchatka for 2008 to 2014
observations. Earth Planets Space 66:150. doi:10.1186/s40623-014-0150-6
Cherniak I, Zakharenkova I, Krankowski A (2014) Approaches for modelingionosphere irregularities based on the TEC rate index. Earth Planets Space
66:165. doi:10.1186/s40623-014-0165-z
Elias AG (2014) Filtering ionosphere parameters to detect trends linked toanthropogenic effects. Earth Planets Space 66:113. doi:10.1186/1880-5981-66-113
Elias AG, de Haro Barbas BF, Shibasaki K, Souza JR (2014) Effect of solar cycle 23
in foF2 trend estimation. Earth Planets Space 66:111. doi:10.1186/1880-598166-111
Forbes JM, Zhang X, Bruinsma SL (2014) New perspectives on thermospheretides: 2. Penetration to the upper thermosphere. Earth Planets Space 66:122.
doi:10.1186/1880-5981-66-122
Fox P, Kozyra J (2015) eScience and Informatics for international science programs.
Prog Earth Planet Sci 2(12):2015. doi:10.1186/s40645-015-0042-9
Fytterer T, Arras C, Hoffmann P, Jacobi C (2014) Global distribution of the migrating
terdiurnal tide seen in sporadic E occurrence frequencies obtained from GPS
radio occultations. Earth Planets Space 66:79. doi:10.1186/1880-5981-66-79
Gan Q, Du J, Ward WE, Beagley SR, Fomichev VI, Zhang S (2014) Climatology ofthe diurnal tides from eCMAM30 (1979 to 2010) and its comparison with
SABER. Earth Planets Space 66:103. doi:10.1186/1880-5981-66-103
Gavrilov NM, Kshevetskii SP (2014) Three-dimensional numerical simulation of
nonlinear acoustic-gravity wave propagation from the troposphere to thethermosphere. Earth Planets Space 66:88. doi:10.1186/1880-5981-66-88
Gopalswamy N, Xie H, Akiyama S, Mäkelä PA, Yashiro S (2014) Major solar eruptions
and high-energy particle events during solar cycle 24. Earth Planets Space
66:104. doi:10.1186/1880-5981-66-104
Gopalswamy N, Tsurutani B, Yan Y (2015) Short-term variability of the Sun-Earthsystem: an overview of progress made during the CAWSES-II period. Prog
Earth Planet Sci 2:13. doi:10.1186/s40645-015-0043-8
Gordiyenko GI, Vodyannikov VV, Yakovets AF, Litvinov YG (2014) A long-term
trend in the F2-layer critical frequency as observed at Alma-Ata ionosonde
station. Earth Planets Space 66:125. doi:10.1186/1880-5981-66-125
Hamid NSA, Liu H, Uozumi T, Yumoto K, Veenadhari B, Yoshikawa A, Sanchez JA(2014) Relationship between the equatorial electrojet and global Sq currents
at the dip equator region. Earth Planets Space 66:146. doi:10.1186/s40623014-0146-2
Iwai K, Shibasaki K, Nozawa S, Takahashi T, Sawada S, Kitagawa J, Miyawaki S,
Kashiwagi H (2014) Coronal magnetic field and the plasma beta determinedfrom radio and multiple satellite observations. Earth Planets Space 66:149.
doi:10.1186/s40623-014-0149-z
Jun C-W, Shiokawa K, Connors M, Schofield I, Poddelsky I, Shevtsov B (2014) Study of
Pc1 pearl structures observed at multi-point ground stations in Russia, Japan,
and Canada. Earth Planets Space 66:140. doi:10.1186/s40623-014-0140-8
Kondoh K, Shimizu T (2014) Study of plasma flow reversal in the near-Earthplasma sheet using numerical computations. Earth Planets Space 66:147.
doi:10.1186/s40623-014-0147-1
Kozai M, Munakata K, Kato C, Kuwabara T, Bieber JW, Evenson P, Rockenbach M,
Lago AD, Schuch NJ, Tokumaru M, Duldig ML, Humble JE, Sabbah I, Al Jassar HK,
Sharma MM, Kota J (2014) The spatial density gradient of galactic cosmic rays
and its solar cycle variation observed with the Global Muon Detector Network.
Earth Planets Space 66:15. doi:10.1186/s40623-014-0151-5
Kumar A, Kumar S (2014) Space weather effects on the low latitude D-region
ionosphere during solar minimum. Earth Planets Space 66:76. doi:10.1186/
1880-5981-66-76
Laskar FI, Pallamraju D, Veenadhari B (2014) Vertical coupling of atmospheres:dependence on strength of sudden stratospheric warming and solar activity.
Earth Planets Space 66:94. doi:10.1186/1880-5981-66-94
Laštovička J, Beig G, Marsh DR (2014) Response of the mesosphere-thermosphereionosphere system to global change—CAWSES-II contribution. Prog Earth
Planet Sci 1:21. doi:10.1186/s40645-014-0021-6
Lopez D, Matsubara Y (2015) Search for solar neutrons at Mount Chacaltayaassociated with M- and X-class flares during the rising period of solar cycle
24. Earth Planets Space 67:54. doi:10.1186/s40623-015-0222-2
Mandrikova OV, Solovev IS, Zalyaev TL (2014) Methods of analysis of geomagnetic
field variations and cosmic ray data. Earth Planets Space 66:148. doi:10.1186/
s40623-014-0148-0
Martinez-Calderon C, Shiokawa K, Miyoshi Y, Ozaki M, Schofield I, Connors M (2015)
Polarization analysis of VLF/ELF waves observed at subauroral latitudes during the
VLF-CHAIN campaign. Earth Planets Space 67:21. doi:10.1186/s40623-014-0178-7

Based on this vast range of achievements fromCAWSES-II, SCSOTEP launched the next international
project named “Variability of the Sun and Its Terrestrial
Impact (VarSITI)” in January 2014. VarSITI is a 5-year
program to understand the variability of solar activity
and its consequences for the Earth. It will cover various
time scales, from the order of thousands of years to milliseconds, and various locations and their connection
from the solar interior to the Earth’s atmosphere (http://
www.varsiti.org/). We continue to investigate further
challenges in order to develop a better understanding of
the Sun-Earth system.
Competing interests
The authors declare that they have no competing interests.
Authors’ contributions
All authors of this article worked as the conveners of the International
CAWSES-II Symposium and served as guest editors for this special issue. Thispreface was prepared by Mamoru Yamamoto, revised by Kazuo Shiokawa
and Nat Gopalswamy, and agreed upon by all authors. All authors read andapproved the final manuscript.
Acknowledgements
We thank all of the participants of the International CAWSES-II Symposium
and give special acknowledgement to all of the authors of the papers in our
special issue. We highly appreciate all referees who served in evaluating thepapers and giving the authors helpful comments and suggestions.
Author details
1
Research Institute for Sustainable Humanosphere (RISH), Kyoto University,
Gokasho, Uji, Kyoto 611-0011, Japan. 2Institute for Space-Earth Environmental
Research (ISEE), Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8601,
Japan. 3National Institute of Polar Research, 10-3, Midori-cho, Tachikawa-shi,
Tokyo 190-8518, Japan. 4Solar Physics Laboratory, Code 671, Heliophysics
Division, NASA Goddard Space Flight Center, Greenbelt, MD 20771, USA.
Received: 22 January 2016 Accepted: 23 January 2016

References
Abadi P, Otsuka Y, Tsugawa T (2015) Effects of pre-reversal enhancement of EXB
drift on the latitudinal extension of plasma bubble in Southeast Asia. Earth
Planets Space 67:74. doi:10.1186/s40623-015-0246-7
Abdu MA, Brum CGM, Batista PP, Gurubaran S, Pancheva D, Bageston JV, Batista IS,
Takahashi H (2015) Fast and ultrafast Kelvin wave modulations of the equatorial
evening F region vertical drift and spread F development. Earth Planets Space
67:1. doi:10.1186/s40623-014-0143-5
Abe S, Umemura N, Koyama Y, Tanaka Y, Yagi M, Yatagai A, Shinbori A, UeNo S,
Sato Y, Kaneda N (2014) Progress of the IUGONET system—metadata databasefor upper atmosphere ground-based observation data. Earth Planets Space
66:133. doi:10.1186/1880-5981-66-133

7International CAWSES-II Symposium
Yamamoto et al. Earth, Planets and Space (2016) 68:26

Page 8 of 8

Muraki Y, Mitsutani T, Shibata S, Kuramata S, Masuda K, Nagaya K (2015) Regional
climate pattern during two millennia estimated from annual tree rings ofYaku cedar trees: a hint for solar variability? Earth Planets Space 67:31. doi:10.
1186/s40623-015-0198-y
Narayanan VL, Sau S, Gurubaran S, Shiokawa K, Balan N, Emperumal K, Sripathi S(2014) A statistical study of satellite traces and evolution of equatorial spread
F. Earth Planets Space 66:160. doi:10.1186/s40623-014-0160-4
Oberheide J, Shiokawa K, Gurubaran S, Ward WE, Fujiwara H, Kosch MJ, Makela JJ,
Takahashi H (2015) The geospace response to variable inputs from the lower
atmosphere: a review of the progress made by Task Group 4 of CAWSES-II.
Prog Earth Planet Sci 2:2. doi:10.1186/s40645-014-0031-4
Oinats AV, Kurkin VI, Nishitani N (2015) Statistical study of medium-scale travelingionospheric disturbances using SuperDARN Hokkaido ground backscatterdata for 2011. Earth Planets Space 67:22. doi:10.1186/s40623-015-0192-4
Pertsev N, Dalin P, Perminov V, Romejko V, Dubietis A, Balčiunas R, Černis K,
Zalcik M (2014) Noctilucent clouds observed from the ground: sensitivity tomesospheric parameters and long-term time series. Earth Planets Space
66:98. doi:10.1186/1880-5981-66-98
Prikryl P, Jayachandran PT, Mushini SC, Richardson IG (2014) High-latitude GPSphase scintillation and cycle slips during high-speed solar wind streams andinterplanetary coronal mass ejections: a superposed epoch analysis. Earth
Planets Space 66:62. doi:10.1186/1880-5981-66-62
Ren Z, Wan W, Xiong J, Liu L (2014) Influence of DE3 tide on the equinoctial
asymmetry of the zonal mean ionospheric electron density. Earth Planets
Space 66:117. doi:10.1186/1880-5981-66-117
Sasai Y, Nagai Y, Itow Y, Matsubara Y, Sako T, Lopez D, Itow T, Munakata K, Kato C,
Kozai M, Miyazaki T, Shibata S, Oshima A, Kojima H, Tsuchiya H, Watanabe K,
Koi T, Valdes-Galicia JF, González LX, Ortiz E, Musalem O, Hurtado A, Garcia R,
Anzorena M (2014) Performance of the SciBar cosmic ray telescope (SciCRT)
toward the detection of high-energy solar neutrons in solar cycle 24. Earth
Planets Space 66:130. doi:10.1186/1880-5981-66-130
Seppälä A, Matthes K, Randall CE, Mironova IA (2014) What is the solar influenceon climate? Overview of activities during CAWSES-II. Prog Earth Planet Sci
1:24. doi:10.1186/s40645-014-0024-3
Shinbori A, Koyama Y, Nose M, Hori T, Otsuka Y, Yatagai A (2014) Long-term
variation in the upper atmosphere as seen in the geomagnetic solar quiet
daily variation. Earth Planets Space 66:155. doi:10.1186/s40623-014-0155-1
Shiokawa K, Otsuka Y, Lynn KJ, Wilkinson P, Tsugawa T (2015) Airglow-imaging
observation of plasma bubble disappearance at geomagnetically conjugate
points. Earth Planets Space 67:43. doi:10.1186/s40623-015-0202-6
Shpynev BG, Kurkin VI, Ratovsky KG, Chernigovskaya MA, Belinskaya AY,
Grigorieva SA, Stepanov AE, Bychkov VV, Pancheva D, Mukhtarov P (2015)
High-midlatitude ionosphere response to major stratospheric warming. Earth
Planets Space 67:18. doi:10.1186/s40623-015-0187-1
Smirnov S (2014) Reaction of electric and meteorological states of the near-groundatmosphere during a geomagnetic storm on 5 April 2010. Earth Planets Space
66:154. doi:10.1186/s40623-014-0154-2
Su S-Y, Wu CL, Liu CH (2014) Correlation between the global occurrences ofionospheric irregularities and deep atmospheric convective clouds in theintertropical convergence zone (ITCZ). Earth Planets Space 66:134. doi:10.
1186/1880-5981-66-134
Truskowski AO, Forbes JM, Zhang X, Palo SE (2014) New perspectives onthermosphere tides: 1. Lower thermosphere spectra and seasonal-latitudinal
structures. Earth Planets Space 66:136. doi:10.1186/s40623-014-0136-4
Tsuda T, Shepherd M, Gopalswamy N (2015) Advancing the understanding of the
Sun-Earth interaction—the Climate and Weather of the Sun-Earth System(CAWSES) II program. Prog Earth Planet Sci 2:28. doi:10.1186/s40645-015-0059-0
Uwamahoro J, Habarulema JB (2014) Empirical modeling of the storm time
geomagnetic indices: a comparison between the local K and global Kp
indices. Earth Planets Space 66:95. doi:10.1186/1880-5981-66-95
Yatagai A, Sato Y, Shinbori A, Abe S, Ueno S, IUGONET project team (2015) The
capacity-building and science-enabling activities of the IUGONET for thesolar-terrestrial research community. Earth Planets Space 67:2. doi:10.1186/
s40623-014-0170-2

8

Earth, Planets and SpaceFRONTIER LETTER Open AccessCorrelation between the global occurrences of ionosphericirregularities and deep atmospheric convective clouds
in the intertropical convergence zone (ITCZ)
Shin-Yi Su*, Chung Lung Wu and Chao Han Liu
Earth, Planets and Space 2014, 66:134 doi:10.1186/1880-5981-66-134
Received: 4 March 2014, Accepted: 24 September 2014, Published: 6 November 2014

Abstract
To study the seeding mechanism of ionospheric irregularity occurrences, a correlation study has been carried out between the
global monthly/latitudinal (m/l) distributions of irregularity occurrences and the deep atmospheric convective clouds in theintertropical convergence zone (ITCZ) indicated by the outgoing longwave radiation (OLR) measurements. Seven longitudesectors - the African, Indian, West Pacific, Central Pacific, East Pacific, South American, and Atlantic sectors - are selected to
study the correlations between the two distributions. The results indicate that good correlations exist only in the SouthAmerican sector and to some extent in the African sector. For the other five sectors, no correlations are found in the m/l
distributions between the irregularities and OLRs. This implies that the gravity wave induced in the ITCZ cannot be the soleseeding agent for the Rayleigh-Taylor (RT) instability in the global irregularity occurrences every season. We suspect that the
post-sunset ionospheric electrodynamic perturbations could be the prevailing seeds for the RT instability globally year long.
Together with the favorable post-sunset ionospheric condition, the global m/ldistributions of irregularity occurrences could be adequately explained.

Keywords: Ionospheric density irregularity; Gravity wave; OLR; ITCZ

Figure 1*Corresponding author: Shin-Yi Su, sysu@jupiter.ss.ncu.edu.tw

FRONTIER LETTER Open AccessCoronal magnetic field and the plasma beta determined from radio
and multiple satellite observations
Kazumasa Iwai*, Kiyoto Shibasaki, Satoshi Nozawa, Takuya Takahashi, Shinpei Sawada, Jun Kitagawa, Shun Miyawaki
and Hirotaka Kashiwagi
Earth, Planets and Space 2014, 66:149 doi:10.1186/s40623-014-0149-z
Received: 3 March 2014, Accepted: 29 October 2014, Published: 14 November 2014

Abstract
We derived the coronal magnetic field, plasma density, and temperature from the observation of polarization and intensity ofradio thermal free-free emission using the Nobeyama Radioheliograph (NoRH) and extreme ultraviolet (EUV) observations. We
observed a post-flare loop on the west limb on 11 April 2013. The line-of-sight magnetic field was derived from the circularly
polarized free-free emission observed by NoRH. The emission measure and temperature were derived from the AtmosphericImaging Assembly (AIA) onboard Solar Dynamics Observatory (SDO). The derived temperature was used to estimate theemission measure from the NoRH radio free-free emission observations. The derived density from NoRH was larger than that
determined using AIA, which can be explained by the fact that the low-temperature plasma is not within the temperature
coverage of the AIA filters used in this study. We also discuss the other observation of the post-flare loops by the EUV Imager
onboard the Solar Terrestrial Relations Observatory (STEREO), which can be used in future studies to reconstruct the coronalmagnetic field strength. The derived plasma parameters and magnetic field were used to derive the plasma beta, which is aratio between the magnetic pressure and the plasma pressure. The derived plasma
beta is about 5.7 × 10−4 to 7.6 × 10−4 at the loop top region.
NoRH 17GHz r+l 11-Apr-2013 02:44:40 UTNoRH 17GHz r-l 11-Apr-2013 02:44:40 UT

1000

11719

11718
11713

0

-500

500
Y (arcsecs)

analysis500
Y (arcsecs)

Keywords: Sun: Corona; Sun: Magnetic fields; Sun: Radio radiation; Methods: Data

1000

0

-500

-1000

-1000
-1000

-500

0
500
X (arcsecs)

1000

Figure 1*Corresponding author: Kazumasa Iwai, kazumasa.iwai@nao.ac.jp
9

-1000

-500

0
500
X (arcsecs)

1000

International CAWSES-II Symposium

FULL PAPER 

Open Access

High-latitude GPS phase scintillation and cycle slips duringhigh-speed solar wind streams and interplanetary coronal massejections: a superposed epoch analysis
Paul Prikryl*, P Thayyil Jayachandran, Sajan C Mushini and Ian G Richardson
Earth, Planets and Space 2014, 66:62 doi:10.1186/1880-5981-66-62
Received: 12 March 2014, Accepted: 12 May 2014, Published: 30 June 2014

Abstract
Results of a superposed epoch (SPE) analysis of occurrence of phase scintillation and cycle slips at high latitudes keyed byarrival times of high-speed solar wind streams (HSS) and interplanetary coronal mass ejections (ICME) for years 2008 to 2012
are presented. Phase scintillation index σΦ is obtained in real time from L1 signal recorded at the rate of 50 Hz by specialized
global positioning system (GPS) ionospheric scintillation and total electron content(TEC) monitors (GISTMs) deployed as a part of the Canadian High Arctic Ionospheric
Network (CHAIN). The phase scintillation, mapped as a function of magnetic latitude
and magnetic local time, occurs predominantly on the dayside in the cusp and in thenightside auroral oval. The scintillation occurrence peaks on days of HSS or ICME
impacts at the Earth’s magnetosphere and tapers off a few days later, which is similar
to day-to-day variability of geomagnetic activity and riometer absorption at highlatitudes. ICMEs that are identified as magnetic clouds are significantly more
geoeffective than HSSs and ICMEs with no or weak magnetic cloud characteristics.
On their arrival day, magnetic clouds result in higher occurrence, and thus
probability, of scintillation in the nightside auroral zone. The SPE analysis results areused to obtain cumulative probability distribution functions for the phase
scintillation occurrence that can be employed in probabilistic forecast of phase
scintillation at high latitudes.

Keywords: Ionosphere; Ionospheric irregularities; GPS scintillation; Solar wind
disturbances; Space weather forecasting

Figure 1*Corresponding author: Paul Prikryl, paul.prikryl@nrcan.gc.ca

FULL PAPER 

Open AccessSpace weather effects on the low latitude D-region ionosphere duringsolar minimum
Abhikesh Kumar* and Sushil Kumar
Earth, Planets and Space 2014, 66:76 doi:10.1186/1880-5981-66-76
Received: 13 March 2014, Accepted: 15 July 2014, Published: 24 July 2014

Abstract
The effects of the solar flares and the geomagnetic storms (disturbance storm time (Dst) < −50 nT) during December 2006 to
2008, a period during the unprecedented solar minimum of solar cycles 23 and 24, have been examined on sub-ionosphericvery low frequency (VLF) signals from NWC (19.8 kHz), NPM (21.4 kHz), VTX (18.2 kHz), and NLK (24.8 kHz) transmittersmonitored at Suva (18.2° S, 178.4° E), Fiji. Apart from the higher class solar flares (C to X), a solar flare of class B8.5 also
produced enhancements both on the amplitude and phase. The amplitude enhancements in NLK, NPM, and NWC signals as afunction of peak solar flare X-ray flux in decibel (dB; relative to 1 μW/m2) shows that the relationship curve is steeper and quite
linear between the flare power levels of 0 to 15 dB; below 0 dB, the curve gets less steep and flattens towards −5 dB flare
power level, while it also gets less steep above 15 dB and almost flattens above 20 dB. In general, the level of amplitudeenhancement for NLK signal is higher than that for NPM and NWC signals for all solar flares. The enhancement in theamplitude and phase of VLF signals by solar flares is due to the increase in the D-region electron density by the solar flareproduced extra ionization. The modeling of VLF perturbations produced by B8.5 and C1.5 classes of solar flares on 29 January
2007 using LWPC (Long Wave Propagation Capability) V2.1 codes show thatreflection height (H’) was reduced by 0.6 and 1.2 km and the exponential sharpness
factor (β) was raised by 0.010 and 0.005 km−1, respectively. Out of seven storms with
Dst < −50 nT, only the intense storm of 14 to 16 December 2006 with a minimum Dstof −145 nT has shown a clear reduction in the signal strength of NWC and NPM
sub-ionospheric signals due to storm-induced reduction in the D-region electron
density.
54oN

NLK

o

36 N

NPM

18oN

VTX

0o

18oS

Fiji
NWC

Keywords: VLF perturbations; Solar flares; Geomagnetic storms; D-region
ionosphere

36oS
80oE

120oE

160oE

Figure 1*Corresponding author: Abhikesh Kumar, kumar_ab@usp.ac.fj
10

160oW

120oW

Earth, Planets and Space

FULL PAPER 

Open Access

Global distribution of the migrating terdiurnal tide seen in sporadic E
occurrence frequencies obtained from GPS radio occultations
Tilo Fytterer*, Christina Arras, Peter Hoffmann and Christoph Jacobi
Earth, Planets and Space 2014, 66:79 doi:10.1186/1880-5981-66-79
Received: 30 March 2014, Accepted: 9 July 2014, Published: 28 July 2014

Abstract

Keywords: Sporadic E layer; Terdiurnal tide; Wind shear theory; GPS radio
occultation

Radio occultations

Global Positioning System radio occultation measurements by FORMOsa SATellite mission-3/Constellation Observing System
for Meteorology, Ionosphere and Climate satellites were used to analyse the characteristics of the 8-h oscillation in sporadic E(ES) layers. Six-year averages based on the 3-monthly mean zonal means from December 2006 to November 2012 wereconstructed for the amplitude of the terdiurnal oscillation in the occurrence frequency of ES. A global distribution from 60° S
to 60° N is given, revealing two peaks above 100 km during solstice with one maximum at low and midlatitudes(approximately 10° to 40°) in each hemisphere. During equinox, the global distribution is marked by two dominant peaks
centred at midlatitudes, while an additional weak maximum is located at very low southern latitudes. The seasonal
characteristics around 110 km reveal large values during equinox at low and midlatitudes (<40° N), while further peaks occur
in April at >40° S and in July near 30° S. The pattern around 90 km is dominated by a
35000
broad peak between 20° and 30° S from March to September. Comparisons with the
30000
terdiurnal oscillation in the neutral atmosphere derived from zonal wind and vertical
25000
zonal wind shear simulated with a circulation model of the middle atmosphere, as
20000
well as with satellite observations of the terdiurnal tide in temperature, fit quite wellfor the results above 100 km, but do not show agreement for lower altitudes.
15000
10000
5000
0

2007
2010

-80 -60 -40 -20

2008
2011

2009
2012

0

40

20

Latitude [°]60

80

Figure 1*Corresponding author: Tilo Fytterer, tilo.fytterer@kit.edu

FULL PAPER 

Open Access

Vertical coupling of atmospheres: dependence on strengthof sudden stratospheric warming and solar activity
Fazlul I Laskar*, Duggirala Pallamraju and Bhaskara Veenadhari
Earth, Planets and Space 2014, 66:94 doi:10.1186/1880-5981-66-94
Received: 30 April 2014, Accepted: 7 August 2014, Published: 18 August 2014

Abstract
Comprehensive behavior of the low-latitude upper atmosphere during sudden stratospheric warming (SSW) events at varying
levels of solar activity has been investigated. The equatorial electrojet (EEJ) strength and the total electron content (TEC) datafrom low latitudes over Indian longitudes during the mid-winter season in the years 2005 to 2013 are used in this study. Five
major and three minor SSW events occurred in the observation duration, wherein the solar activity had varied from minimum(almost no sunspots) to mini-maximum (approximately 50 sunspots of the solar cycle 24). Spectral powers of the large-scaleplanetary wave (PW) features in the EEJ and the TEC have been found to be varying with solar activity and SSW strengths.
Specially, the spectral powers of quasi-16-day wave variations during the three very strong SSW events in the years 2006,
2009, and 2013 were found to be very high in comparison with those of other years. For these major events, the amplitudes ofthe semi-diurnal tides and quasi-16-day waves were found to be highly correlated
and were maximum around the peak of SSW, suggesting a strong interaction
between the two waves. However, this correlation was poor and the quasi-16-day
spectral power was low for the minor events. A strong coupling of atmospheres wasnoted during a relatively high solar activity epoch of 2013 SSW, which was, however,explained to be due to the occurrence of a strong SSW event. These results suggestthat the vertical coupling of atmospheres is stronger during strong major SSW
events and these events play an important role in enabling the coupling even duringhigh solar activity.

Keywords: Sudden stratospheric warming; Planetary waves; Atmospheric tides;

Total electron content; Sun-Earth interaction; Vertical coupling; Upper
atmosphere; Ionosphere; Thermosphere*Corresponding author: Fazlul I Laskar, fazlul84@gmail.com
11

Figure 1

International CAWSES-II Symposium

FULL PAPER 

Open Access

Empirical modeling of the storm time geomagnetic indices:
a comparison between the local K and global Kp indicesJean Uwamahoro* and John Bosco Habarulema
Earth, Planets and Space 2014, 66:95 doi:10.1186/1880-5981-66-95
Received: 1 April 2014, Accepted: 6 August 2014, Published: 20 August 2014

Abstract
This paper describes a neural network-based model developed to predict geomagnetic storms time K index as measured at amagnetic observatory located in Hermanus (34°25 S; 19°13 E), South Africa. The parameters used as inputs to the neuralnetwork were the solar wind particle density N, the solar wind velocity V, the interplanetary magnetic field (IMF) total average
field Bt as well as the IMF Bz component. Averaged hourly OMNI-2 data comprising storm periods extracted from solar cycle 23(SC23) were used to train the neural network. The prediction performance of this model was tested on some moderate tosevere storms (with K ≥ 5) that were not included in the training data set and the results are compared to the prediction of the
global geomagnetic Kp index. The model results show a good predictability of the
K−index measurements: Magnetic storm on 3−4 /08/2010
Hermanus storm time K index with a correlation coefficient of 0.8.
98

Keywords: Solar wind; Geomagnetic indices; Neural networks
K−index level

7
6
5
4

CME

3
2
1
0

1

2
3
4
First 6 days, August 2010

5

6

Figure 1*Corresponding author: Jean Uwamahoro, mahorojpacis@gmail.com

FULL PAPER 

Open AccessClimatology of the diurnal tides from eCMAM30 (1979 to 2010)
and its comparison with SABER
Quan Gan*, Jian Du, William E Ward, Stephen R Beagley, Victor I Fomichev and Shaodong Zhang
Earth, Planets and Space 2014, 66:103 doi:10.1186/1880-5981-66-103
Received: 31 March 2014, Accepted: 16 August 2014, Published: 28 August 2014

Abstract

Keywords: Diurnal tides; Migrating; Nonmigrating; eCMAM30; SABER;QBO*Corresponding author: Quan Gan, quan.gan@louisville.edu
12

110
100
90
80
70
60
50
40
30
20
-90

300
280
260
240
220
200
180

Altitude (km)Altitude (km)The extended Canadian Middle Atmosphere Model (eCMAM) was recently run in a nudged mode using reanalysis data fromthe ground to 1 hPa for the period of January 1979 to June 2010 (hence the name eCMAM30). In this paper, eCMAM30
temperature is used to examine the background mean temperature, the spectrum of the diurnal tides, and the climatology ofthe migrating diurnal tide Dw1 and three nonmigrating diurnal tides De3, Dw2, and Ds0 in the stratosphere, mesosphere, andlower thermosphere. The model results are then compared to the diurnal tidal climatology derived from Sounding of the
Atmosphere using Broadband Emission Radiometry (SABER) observations between 40 to 110 km and 50° S to 50° N fromJanuary 2002 to December 2013. The model reproduces the latitudinal background mean temperature gradients well exceptthat the cold mesopause temperature in eCMAM30 is 10 to 20 K colder than SABER. The diurnal tidal spectra and their relative
strengths compare very well between eCMAM30 and SABER. The altitude-latitude structures for the four diurnal tidal
components (Dw1, De3, Dw2, and Ds0) from the two datasets are also in very good agreement even for structures in thestratosphere with a weaker amplitude. The largest discrepancy between the model and SABER is associated with the seasonalvariation of De3. In addition to the Northern Hemisphere (NH) summer maximum, a secondary maximum occurs during NH
winter (December-February) in the model but is absent in SABER. The seasonal variations of the other three diurnal tidal
components are in good agreement. Interannual time series of Dw1
eCMAM30
SABER
SpringSpringand De3 from both eCMAM30 and SABER reveal variability with aperiod of 25 to 26 months, which indicates the modulation of thediurnal tides by the stratospheric quasi-biennial oscillation (QBO).
200
220
240
260

260
240

220

-60

-30

0
30
Latitude (deg)

60

90

110
100
90
80
70
60
50
40
30
20
-90

Figure 1

280
260
240
220
200
180

200

220

240

260

240

220

-60

-30

0
30
Latitude (deg)6090Earth, Planets and Space

FULL PAPER 

Open Access

Major solar eruptions and high-energy particle events during solar
cycle 24
Nat Gopalswamy*, Hong Xie, Sachiko Akiyama, Pertti A Mäkelä and Seiji Yashiro
Earth, Planets and Space 2014, 66:104 doi:10.1186/1880-5981-66-104
Received: 10 April 2014, Accepted: 14 August 2014, Published: 1 September 2014

Abstract
We report on a study of all major solar eruptions that occurred on the frontside of the Sun during the rise to peak phase of cycle 24(first 62 months) in order to understand the key factors affecting the occurrence of large solar energetic particle events (SEPs) andground level enhancement (GLE) events. The eruptions involve major flares with soft X-ray peak flux ≥ 5.0 x10−5 Wm−2 (i.e., flare size ≥M5.0) and accompanying coronal mass ejections (CMEs). The selection criterion was based on the fact that the only front-side GLE incycle 24 (GLE 71) had a flare size of M5.1. Only approximately 37% of the major eruptions from the western hemisphere resulted inlarge SEP events. Almost the same number of large SEP events was produced in weaker eruptions (flare size < M5.0), suggesting thatthe soft X-ray flare is not a good indicator of SEP or GLE events. On the other hand, the CME speed is a good indicator of SEP and GLE
events because it is consistently high supporting the shock acceleration mechanism. We found the CME speed, magnetic connectivity
to Earth (in longitude and latitude), and ambient conditions as the main factors that contribute to the lack of high-energy particle
events during cycle 24. Several eruptions poorly connected to Earth (eastern-hemisphere or behind-the-west-limb events) resulted invery large SEP events detected by the Solar Terrestrial Relations Observatory (STEREO) spacecraft. Some very fast CMEs, likely to haveaccelerated particles to GeV energies, did not result in a GLE event because of poor
latitudinal connectivity. The stringent latitudinal requirement suggests that the highest(a)(b)
energy particles are likely accelerated in the nose part of shocks, while the lower energy
CMEparticles are accelerated at all parts. There were also well-connected fast CMEs, which did
not seem to have accelerated high-energy particles due to possible unfavorable ambientconditions (high Alfven speed, overall reduction in acceleration efficiency in cycle 24).

Keywords: Coronal mass ejections; Flares; Ground level enhancement events; Solarenergetic particle events

N17W36
SOHO: 2011/08/04 04:00

SOHO: 2011/08/04 04:12

Figure 1*Corresponding author: Nat Gopalswamy, nat.gopalswamy@nasa.gov

FULL PAPER 

Open Access

Effect of solar cycle 23 in foF2 trend estimation
Ana G Elias*, Blas F de Haro Barbas, Kiyoto Shibasaki and Jonas R Souza
Earth, Planets and Space 2014, 66:111 doi:10.1186/1880-5981-66-111
Received: 27 April 2014, Accepted: 22 August 2014, Published: 10 September 2014

Abstract
The effect of including solar cycle 23 in foF2 trend estimation is assessed using experimental values for Slough (51.5°N,
359.4°E) and Kokobunji (35.7°N, 139.5°E), and values obtained from two models: (1) the Sheffield University PlasmasphereIonosphere model, SUPIM, and (2) the International Reference Ionosphere, IRI. The dominant influence on the F2 layer is solar
extreme ultraviolet (EUV) radiation, evinced by the almost 90% variance of its parameters explained by solar EUV proxies suchas the solar activity indices Rz and F10.7. This makes necessary to filter out solar activity effects prior to long-term trend
estimation. Solar cycle 23 seems to have had an EUV emission different from that deduced from traditional solar EUV proxies.
During maximum and descending phase of the cycle, Rz and F10.7 seem to underestimate EUV solar radiation, while during
minimum, they overestimate EUV levels. Including this solar cycle in trend estimations then, and using traditional filtering
techniques, may induce some spurious results. In the present work, filtering is done in the usual way considering the residualsof the linear regression between foF2 and F10.7, for both experimental and modeled
values. foF2 trends become less negative as we include years after 2000, since foF2
asystematically exceeds the values predicted by a linear fit between foF2 and F10.7.
Trends become more negative again when solar cycle 23 minimum is included, sincefor this period, foF2 is systematically lower than values predicted by the linear fit.
foF2 trends assessed with modeled foF2 values are less strong than those obtainedwith experimental foF2 values and more stable as solar cycle 23 is included in thetrend estimation. Modeled trends may be thought of as a ‘zero level’ trend due to theassumptions made in the process of trend estimation considering also that we are
not dealing with ideal conditions or infinite time series.

Keywords: Ionospheric trends; Solar cycle 23; EUV proxies

Figure 1*Corresponding author: Ana G Elias, anagelias@yahoo.com
13(c) WIND/WAVESType II

International CAWSES-II Symposium

FULL PAPER 

Open Access

Filtering ionosphere parameters to detect trends linked
to anthropogenic effects
Ana G Elias
Earth, Planets and Space 2014, 66:113 doi:10.1186/1880-5981-66-113
Received: 8 April 2014, Accepted: 22 August 2014, Published: 10 September 2014

Abstract
The great concern about the global warming observed in the troposphere has generated a large interest in the study of long-term
trends in the ionosphere since the early 1990s, which has now become a significant topic in global change investigations. Some
research works link ionosphere trends to anthropogenic sources such as the increase in greenhouse gas concentration, and others tonatural causes such as solar and geomagnetic activity long-term changes, and secular variations in the Earth’s main magnetic field. In
all the cases, in order to analyze ionospheric trends, solar activity effect must be filtered out first since around 90% of ionosphereparameter variance is due to solar variations. The filtering process can generate ‘spurious’ trends in the filtered data series which maylead to erroneous conclusions. foF2 data series which include solar cycle 23 are analyzed in the present work in order to detect theeffect of different filtering procedures on the determination of long-term trends. In particular, solar cycle 23 seems to have had an
extreme ultraviolet (EUV) emission greater than that deduced from traditional solar EUV proxies during the maximum epoch andlower during the minimum epoch. When solar activity is filtered assessing the residuals ofa linear regression between foF2 and Rz, or between foF2 and F10.7, this fact may biasatrend values especially because it is at the end of the time series. The length of the period
considered for trend assessment, the saturation and hysteresis effect of some ionosphereparameters, and the solar EUV proxy used are also considered in this study in order toquantify a possible spurious trend that may result as a by-product of a filtering process.
Since trends expected as a consequence of anthropogenic effects are relatively small,these spurious effects may surely mask, or enhance, trends expected from anthropogenic
origins.

Keywords: Long-term trends; Ionosphere; foF2; Solar EUV proxy; Greenhouse effectFigure 1

Corresponding author: Ana G Elias, anagelias@yahoo.com

FULL PAPER 

Open Access

New perspectives on thermosphere tides:
2. Penetration to the upper thermosphere
Jeffrey M Forbes*, Xiaoli Zhang and Sean L Bruinsma
Earth, Planets and Space 2014, 66:122 doi:10.1186/1880-5981-66-122
Received: 1 April 2014, Accepted: 16 August 2014, Published: 25 September 2014

Abstract
In this paper, we present new multi-year and 72-day mean seasonal-latitudinal tidal structures in exospheric temperature
derived from joint analysis of CHAMP and GRACE accelerometer measurements. These results include diurnal tides DE3, DE2,
D0, and DW2 and semidiurnal tides S0, SE1, SE2, SE3, SW4, and SW6. We also employ Hough mode extensions (HMEs) and the
Climatological Model of Thermosphere Tides (CTMT) to ascertain whether the observed structures are consistent with thoseobserved at 110 km and presented in part 1 of this study. The aggregate sum of all the tidal components is shown to impose
considerable longitude and month-to-month variability on the exosphere temperature tidal spectrum.
Please see related article: http://www.earth-planets-space.com/content/66/1/136.

Keywords: Tides; Thermosphere; Dynamics; Propagation

Figure 1*Corresponding author: Jeffrey M Forbes, forbes@colorado.edu
14

Earth, Planets and Space

FULL PAPER 

Open AccessA long-term trend in the F2-layer critical frequency as observedat Alma-Ata ionosonde station
Galina I Gordiyenko*, Victor V Vodyannikov, Artur F Yakovets and Yuriy G Litvinov
Earth, Planets and Space 2014, 66:125 doi:10.1186/1880-5981-66-125
Received: 31 March 2014, Accepted: 3 September 2014, Published: 17 October 2014

Abstract

Keywords: Upper ionosphere; Long-term changes (trends); Solar-ionosphereinteractions

foF2 (x10), MHz

a

160
140
120
100
80
60
40
15/01/32b
Solar flux, F10.7

In this study, we combine monthly median values for the F2-layer critical frequency(foF2), measured at Alma-Ata ionosonde station [43.25°N, 76.92°E] between 1000
and 1400 (local time), with historical data on the monthly mean values for solar
radio flux at 10.7 cm (F10.7) and the geomagnetic activity index (Ap) (available at
http://www.swpc.noaa.gov/), over the period from 1957 to 2012. These data areused to derive long-term trends in the upper ionosphere and to discuss theirimportance in the context of coupling between solar and geomagnetic activity inthe ionosphere at middle latitudes.

15/01/44

15/01/56

15/01/44

15/01/56

15/01/44

15/01/56

15/01/68

15/01/80

15/01/92

15/01/04

15/01/16

15/01/68

15/01/80

15/01/92

15/01/04

15/01/16

15/01/68

15/01/80

15/01/92

15/01/04

15/01/16

Date (dd/mm/yy)

300
250
200
150
100
50
15/01/32cDate (dd/mm/yy)

50

Ap - index

40
30
20
10
0
15/01/32

Date (dd/mm/yy)

Figure 1*Corresponding author: Galina I Gordiyenko, ggordiyenko@mail.ru

FULL PAPER 

Open AccessStudy of Pc1 pearl structures observed at multi-point ground stations
in Russia, Japan, and Canada
Chae-Woo Jun*, Kazuo Shiokawa, Martin Connors, Ian Schofield, Igor Poddelsky and Boris Shevtsov
Earth, Planets and Space 2014, 66:140 doi:10.1186/s40623-014-0140-8
Received: 28 March 2014, Accepted: 1 October 2014, Published: 23 October 2014

Abstract
We investigate possible generation mechanisms of Pc1 pearl structures using multi-point induction magnetometers in
Athabasca in Canada, Magadan in Russia, and Moshiri in Japan. We selected two Pc1 pulsations that were simultaneously
observed at the three stations and applied a polarization analysis. In case 1, on 8 April 2010, Pc1 pearl structures were slightly
different in some time intervals at different stations, and their polarization angles varied depending on the frequencies at thethree stations. Case 2, on 11 April 2010, showed Pc1 pearl structures that were similar at different stations, and theirpolarization angle was independent of frequency at all three stations. In order to understand these differences, we performed
two simple model calculations of Pc1 pearl structures under different conditions. The first model assumes that Pc1 waves
propagated from a latitudinally extended source with different frequencies at different latitudes to the observation points,
representing beating of these waves in the ionosphere. The second model considers
Pc1 waves for which different frequencies are mixed at a point source to cause thebeating at the source point, indicating that the Pc1 pearl structures are generated in
MGD
ATH(60 N, 150 E)
the magnetosphere. The first model shows slightly different waveforms at different(54.7 N, 246.7 E)
51.9 MLAT
61.7 MLAT(L = 2.63)
stations. In contrast, the second model shows identical waveforms at different(L = 4.45)
stations. From these results, we conclude that, in case 1, Pc1 pearl structures werecaused by beating in the ionosphere. On the other hand, in case 2, they were theMOS(44.3 N, 142.27 E)
result of magnetospheric effects. We suggest that beating processes in the35.6 MLAT(L = 1.51)
ionosphere could be one of the generation mechanisms of Pc1 pearl structures.

Keywords: Pc1 pulsations; Pearl structures; Multi-point ground-based observation*Corresponding author: Chae-Woo Jun, chae-woo@stelab.nagoya-u.ac.jp
15

Figure 1

International CAWSES-II Symposium

FULL PAPER 

Open Access

New perspectives on thermosphere tides: 1. Lower thermosphere
spectra and seasonal-latitudinal structures
Alexander O Truskowski, Jeffrey M Forbes*, Xiaoli Zhang and Scott E Palo
Earth, Planets and Space 2014, 66:136 doi:10.1186/s40623-014-0136-4
Received: 1 April 2014, Accepted: 29 September 2014, Published: 30 October 2014

Abstract
Thermosphere-Ionosphere-Mesosphere Energetics and Dynamics/Sounding of the Atmosphere using Broadband Emission
Radiometry (TIMED/SABER) temperature measurements at 110 km and between ±50° latitude extending from 2002 through2010 are analyzed to reveal the tidal spectrum entering the ionosphere-thermosphere (IT) system. Seasonal-latitudinal
structures are presented for the most prominent spectral components which include DE3, DE2, D0, DW1, DW2, SE1 to SE4,
SW1 to SW4, SW6, TE1, TW4, TW5, and TW7. Referring to recent calculations of lower
atmosphere heat sources as well as vertical structure characteristics of these waves
anticipated from classical tidal theory, we analyze the likely origins of these waves and thenature of their seasonal-latitudinal structures. Several waves are likely to arise throughnonlinear wave-wave interactions, and in some cases, this appears to be the sole viablemechanism leading to their existence. The tidal spectrum quantified here is especiallyrelevant to the dynamo generation of electric fields which then impose the tidal variabilityon the overlying F-region ionosphere. Part 2 of this 2-part study examines penetration of
the tidal spectrum to the upper thermosphere.
Please see related article: http://www.earth-planets-space.com/content/66/1/122.

Keywords: Tides; Thermosphere; Dynamics; Propagation

Figure 1*Corresponding author: Jeffrey M Forbes, forbes@colorado.edu

FULL PAPER 

Open AccessA statistical study of satellite traces and evolutionof equatorial spread F
Viswanathan Lakshmi Narayanan*, Sukanta Sau, Subramanian Gurubaran, Kazuo Shiokawa, Nanan Balan,Kaliappan Emperumal and Samireddipalle Sripathi
Earth, Planets and Space 2014, 66:160 doi:10.1186/s40623-014-0160-4
Received: 30 April 2014, Accepted: 14 November 2014, Published: 3 December 2014

Abstract
The ionosonde observations made at 5-min intervals at the Indian dip equatorial station Tirunelveli (8.7°N, 77.8°E geographic;
1.1°N dip latitude) from March 2008 to February 2009 during the extended solar minimum period are used to study theinterlink between equatorial spread F (ESF) and satellite traces (STs) which are assumed to represent tilts in the bottomside
iso-electron density surfaces probably caused by large-scale wave-like structures (LSWS).
The data show different patterns of ESF onset in the bottomside F region, which areillustrated through examples. In addition, the statistics of occurrence of ST and its relation
to the formation of ESF are studied. The results indicate that (1) the zonally drifting ESF
irregularities can be differentiated from those forming over the observing station. (2) Nearly
half of the ESF events were preceded by ST. (3) In about 30% of the cases of occurrence of
ST, ESF was not formed afterwards implying that LSWS may not always lead to ESF. (4) The
percentage of ESF following ST was high in summer and increased with the time of thenight. (5) Following the first occurrence of ST, the ESF onset was delayed by about 30 min
on the average suggesting that ST may be used as a precursor of ESF. (6) Pre-reversal
enhancement (PRE) of upward plasma drift was found insignificant during the period ofstudy. The trapping of high-frequency radio waves between the E and F regions during
intense sporadic E is also illustrated.

Keywords: Ionosonde; Equatorial spread F; Plasma bubbles; Satellite traces; Large-scalewave-like structures

Altitude (km)

6 0 0

4 0 0

2 0 0

0

1

M

H

z

Figure 1*Corresponding author: Viswanathan L Narayanan, narayananvlwins@gmail.com
16

1 0

Earth, Planets and Space

FULL PAPER 

Open AccessLong-term variation in the upper atmosphere as seenin the geomagnetic solar quiet daily variation
Atsuki Shinbori*, Yukinobu Koyama, Masahito Nose, Tomoaki Hori, Yuichi Otsuka and Akiyo Yatagai
Earth, Planets and Space 2014, 66:155 doi:10.1186/s40623-014-0155-1
Received: 28 March 2014, Accepted: 11 November 2014, Published: 11 December 2014

Abstract
Characteristics of long-term variation in the amplitude of solar quiet (Sq) geomagnetic field daily variation have been
investigated using 1-h geomagnetic field data obtained from 69 geomagnetic observation stations within the period of 1947
to 2013. The Sq amplitude observed at these geomagnetic stations showed a clear dependence on the 10- to 12-year solar
activity cycle and tended to be enhanced during each solar maximum phase. The Sq amplitude was the smallest around theminimum of solar cycle 23/24 in 2008 to 2009. The relationship between the solar F10.7 index and Sq amplitude wasapproximately linear but about 53% of geomagnetic stations showed a weak nonlinear relation to the solar F10.7 index. In
order to remove the effect of solar activity seen in the long-term variation of the Sq amplitude, we calculated a linear or
second-order fitting curve between the solar F10.7 index and Sq amplitude during 1947 to 2013 and examined the residual Sq
amplitude, which is defined as the deviation from the fitting curve. As a result, the majority of trends in the residual Sq
amplitude that passed through a trend test showed negative values over a wide region. This tendency was relatively strong inEurope, India, the eastern part of Canada, and New Zealand. The relationshipbetween the magnetic field intensity at 100-km altitude and residual Sq amplitude
showed an anti-correlation for about 71% of the geomagnetic stations. Furthermore,
the residual Sq amplitude at the equatorial station (Addis Ababa) was anti-correlatedwith the absolute value of the magnetic field inclination. This implies movement of
the equatorial electrojet due to the secular variation of the ambient magnetic field.

Keywords: Solar quiet geomagnetic field daily variation; Solar activity; Long-term
trend; Secular variation; Upper atmosphere

Figure 1*Corresponding author: Atsuki Shinbori, shinbori@rish.kyoto-u.ac.jp

FULL PAPER 

Open AccessFast and ultrafast Kelvin wave modulations of the equatorial evening
F region vertical drift and spread F development
Mangalathayil A Abdu*, Christiano GM Brum, Paulo P Batista, Subramanian Gurubaran, Dora Pancheva,
Jose V Bageston, Inez S Batista and Hisao Takahashi
Earth, Planets and Space 2015, 67:1 doi:10.1186/s40623-014-0143-5
Received: 29 April 2014, Accepted: 14 October 2014, Published: 6 January 2015

Abstract
In this paper, we investigate the role of eastward and upward propagating fast (FK) and ultrafast Kelvin (UFK) waves in the
day-to-day variability of equatorial evening prereversal vertical drift and post sunset generation of spread F/plasma bubble
irregularities. Meteor wind data from Cariri and Cachoeira Paulista (Brazil) and medium frequency (MF) radar wind data from
Tirunelveli (India) are analyzed together with Thermosphere-Ionosphere-Mesosphere Energetics and Dynamics/Sounding of
the Atmosphere using Broadband Emission Radiometry (TIMED/SABER) temperature in the 40- to 100-km region tocharacterize the zonal and vertical propagations of these waves. Also analyzed are the F region evening vertical drift andspread F (ESF) development features as diagnosed by Digisonde (Lowell Digisonde International, LLC, Lowell, MA, USA)
operated at Fortaleza and Sao Luis in Brazil. The SABER temperature data permitted determination of the upward propagation
characteristics of the FK (E1) waves with propagation speed in the range of 4 km/day. The radar mesosphere and lower
thermosphere (MLT) winds in the widely separated longitude sectors have yielded the eastward phase velocity of both the FK
and UFK waves. The vertical propagation of these waves cause strong oscillation in the F region evening prereversal verticaldrift, observed for the first time at both FK and UFK periodicities. A delay of a few(approximately 10) days is observed in the F region vertical drift perturbation withrespect to the corresponding FK/UFK zonal wind oscillations, or temperatureoscillations in the MLT region, which has permitted a direct identification of thesunset electrodynamic coupling process as being responsible for the generation of
the FK/UFK-induced vertical drift oscillation. The vertical drift oscillations are foundto cause significant modulation in the spread F/plasma bubble irregularity
development. The overall results highlight the role of FK/UFK waves in the day-today variability of the ESF in its occurrence season.
Figure 1
Geographic Latitude

60
40
20

Tirunelveli

Sao Luis
Fortaleza
Cariri0-20Cachoeira Paulista

-40
-60

-150

-120

-90

-60

-30

0

30

Geographic Longitude*Corresponding author: Mangalathayil A Abdu, ma.abdu@inpe.br
17

60

90

120

150

International CAWSES-II Symposium

FULL PAPER 

Open AccessPolarization analysis of VLF/ELF waves observed at subauroral
latitudes during the VLF-CHAIN campaign
Claudia Martinez-Calderon*, Kazuo Shiokawa, Yoshizumi Miyoshi, Mitsunori Ozaki, Ian Schofield and Martin Connors
Earth, Planets and Space 2015, 67:21 doi:10.1186/s40623-014-0178-7
Received: 28 March 2014, Accepted: 25 November 2014, Published: 11 February 2015

Abstract

60

60

Chorus wave emissions are one of the most intense naturally occurring phenomena in the very low (VLF) and extremely low
frequency (ELF) ranges. They are believed to be one of the major contributors to acceleration and loss of electrons in theradiation belts. During the VLF Campaign observation with High-resolution Aurora Imaging Network (VLF-CHAIN) from 17 to
25 February 2012, several types of VLF/ELF emissions, including chorus, were observed at subauroral latitudes in Athabasca,
Canada. To our knowledge, there has not been any comprehensive study of the physical properties of such emissions at theselatitudes. In this study, we calculate spectral and polarization parameters of VLF/ELF waves with high temporal resolution. We
found that the polarization angle of several emissions depended on both frequency and time. We suggest that the frequencydependent events, which usually last several tens of minutes, might be the consequence of the broadening of the ray paththat the waves follow from their generation region to the ground. Furthermore, time-dependent events, also lasting tens ofminutes, have a polarization angle that changes from negative to positive values (or
−120
−100
−80
−140
vice versa) every few minutes. We suggest that this could be due to variations of the
75
75
wave duct, either near the generation region or along the wave propagation path.
Using another ground station in Fort Vermillion, Canada, about 450 km northwest of
AURORAL OVAL
70
70
Athabasca, we tracked the movements of the ionospheric exit point of three chorus
Fort Vermillion(58.38 N, 243.99 E)
emissions observed simultaneously at both stations. Although we found that
MLAT=64.5 N
movement of the ionospheric exit point does not follow a general direction, it isAthabasca(54.60 N, 246.36 E)
subject to hovering motion, suggesting that the exit point can be affected by small60
MLAT=61.17 N
60
scale plasma processes.
o

o

o

o

o

50

−120

Keywords: Chorus; Polarization; VLF; ELF; Ionospheric source

50

o

−100

Figure 1*Corresponding author: Claudia Martinez-Calderon, claudia@stelab.nagoya-u.ac.jp

FULL PAPER 

Open AccessAirglow-imaging observation of plasma bubble disappearance
at geomagnetically conjugate points
Kazuo Shiokawa*, Yuichi Otsuka, Kenneth JW Lynn, Philip Wilkinson and Takuya Tsugawa
Earth, Planets and Space 2015, 67:43 doi:10.1186/s40623-015-0202-6
Received: 29 March 2014, Accepted: 3 February 2015, Published: 26 March 2015

Abstract
We report the first observation of the disappearance of a plasma bubble over geomagnetically conjugate points. It wasobserved by airglow imagers at Darwin, Australia (magnetic latitude: −22°N) and Sata, Japan (21°N) on 8 August 2002. The
plasma bubble was observed in 630-nm airglow images from 1530 (0030 LT) to 1800 UT (0300 LT) and disappeared
equatorward at 1800 to 1900 UT (0300 to 0400 LT) in the field of view. The ionograms at Darwin and Yamagawa (20 km northof Sata) show strong spread-F signatures at approximately 16 to 21 UT. At Darwin, the F-layer virtual height suddenly
increased from approximately 200 to approximately 260 km at the time of bubble disappearance. However, a similar F-layerheight increase was not observed over the conjugate point at Yamagawa, indicating that this F-layer rise was caused not by aneastward electric field but by enhancement of the equatorward thermospheric wind
PERCENT-66over Darwin. We think that this enhancement of the equatorward neutral wind was
Darwin 630 nm 8 August 2002
Deviation from 1-h running averages
Exposure: 2m45s
caused by an equatorward-propagating large-scale traveling ionospheric
N 1532:02UT (b)1614:02UT (c)1702:02UT(a)disturbance, which was identified in the north-south keogram of 630-nm airglow
images. We speculate that polarization electric field associated with this equatorwardE
neutral wind drive plasma drift across the magnetic field line to cause the observed
bubble disappearance.
153202(d)174402 (e)1744:02UT(g)

153204 (h)N 1532:04UT

161402

183202 (f)1832:02UT

170202190203
1902:03UT

Keywords: Plasma bubble disappearance; Conjugate observation; Airglow imaging

Figure 1*Corresponding author: Kazuo Shiokawa, shiokawa@stelab.nagoya-u.ac.jp161302 (i)1613:02UT

170212
1702:12UT

183204 (l)1832:04UT

190222
1902:22UT

E

18
(j)

174302 (k)1743:02UT

Earth, Planets and Space

FULL PAPER 

Open Access

Effects of pre-reversal enhancement of E × B drift on the latitudinal
extension of plasma bubble in Southeast Asia
Prayitno Abadi*, Yuichi Otsuka and Takuya Tsugawa
Earth, Planets and Space 2015, 67:74 doi:10.1186/s40623-015-0246-7
Received: 5 June 2014, Accepted: 12 May 2015, Published: 27 May 2015

Abstract
We investigated the effects of the F region bottomside altitude (h’F), maximum upward E × B drift velocity, duration of pre-reversal
enhancement and the integral of upward E × B drift on the latitudinal extension of equatorial plasma bubbles in the Southeast Asian sector
using the observations recorded by three GPS receivers and two ionosondes. The GPS receivers are installed at Kototabang (0.2°S, 100.3°E;
9.9°S magnetic latitude), Pontianak (0.02°S, 109.3°E; 9.8°S magnetic latitude) and Bandung (6.9°S, 107.6°E; 16.7°S magnetic latitude) in
Indonesia. The ionosondes are installed at magnetically equatorial stations, Chumphon (10.7°N, 99.4°E; 0.86°N magnetic latitude) in Thailand
and Bac Lieu (9.3°N, 105.7°E; 0.62°N magnetic latitude) in Vietnam. We analysed those observationsacquired in the equinoctial months (March, April, September and October) in 2010–2012, when thesolar activity index F10.7 was in the range from 75 to 150. Assuming that plasma bubbles are themajor source of scintillations, the latitudinal extension of the bubbles was determined according to
the S4 index. We have found that the peak of h’F, maximum upward E × B drift and the integral of
upward E × B drift during the pre-reversal enhancement period are positively correlated with the
maximum latitude extension of plasma bubbles, but that duration of pre-reversal enhancement
does not show correlation. The plasma bubbles reached magnetic latitudes of 10°–20° in thefollowing conditions: (1) the peak value of h’F is greater than 250–450 km, (2) the maximum upward
E × B drift is greater than 10–70 m/s and (3) the integral of upward E × B drift is greater than 50–
250 m/s. These results suggest that the latitudinal extension of plasma bubbles is controlled mainlyby the magnitude of pre-reversal enhancement and the peak value of h’F at the initial phase ofdevelopment of plasma bubbles (or equatorial spread F) rather than by the duration of pre-reversal
enhancement.

Keywords: Equatorial ionosphere; Plasma bubble; Pre-reversal enhancement;
Scintillation

Figure 1*Corresponding author: Prayitno Abadi, prayabadi@bdg.lapan.go.id

LETTER 

Open AccessThree-dimensional numerical simulation of nonlinear acoustic-gravity
wave propagation from the troposphere to the thermosphere
Nikolai M Gavrilov* and Sergey P Kshevetskii*
Earth, Planets and Space 2014, 66:88 doi:10.1186/1880-5981-66-88
Received: 22 January 2014, Accepted: 22 July 2014, Published: 6 August 2014

Abstract
Three-dimensional nonlinear breaking acoustic-gravity waves (AGWs) propagating from the Earth’s surface to the upper
atmosphere are simulated numerically. Horizontally moving periodical structures of vertical velocity on the Earth’s surface areused as AGW sources in the model. The 3D algorithm for hydrodynamic equation solution uses finite-difference analogues ofbasic conservation laws. This approach allows us to select physically correct generalized wave solutions of hydrodynamic
equations. The numerical simulation covers altitudes from the ground up to 500 km. Vertical profiles of the mean temperature,density, molecular viscosity, and thermal conductivity are specified from standard models of theatmosphere. Atmospheric waves in a few minutes can propagate to high altitudes above 100 km after
activation of the surface wave forcing. Surfaces of constant phases are quasi-vertical first, and thenbecome inclined to the horizon below about 100 km after some transition time interval. Vertical
wavelengths decrease with time and tend to theoretically predicted values after times longer thanseveral periods of the wave forcing. Decrease in vertical wavelengths and increase in AGW amplitudes
can lead to wave instabilities, accelerations of the mean flow and wave-induced jet streams at altitudes
above 100 km. AGWs may transport amplitude modulation of atmospheric wave sources in horizontal
directions up to very high levels. Low wave amplitudes in the beginning of transition processes after
activation of atmospheric wave sources could be additional reasons for slower amplitude grows withheight compared to the nondissipative exponential growth predicted for stationary linear AGWs.
Production of wave-induced mean jets and their superposition with nonlinear unstable dissipative
AGWs can produce strong narrow peaks of horizontal speed in the upper atmosphere. This may increase
the role of transient nonstationary waves in effective energy transport and variations of atmosphericparameters and gas admixtures in a broad altitude range.
Figure 1*Corresponding authors: Nikolai M Gavrilov, n.gavrilov@spbu.ru; Sergey P Kshevetskii, renger@mail.ru
19International CAWSES-II Symposium

LETTER

Open Access

Noctilucent clouds observed from the ground: sensitivity
to mesospheric parameters and long-term time series
Nikolay Pertsev*, Peter Dalin, Vladimir Perminov, Vitaly Romejko, Audrius Dubietis, Ričardas Balčiunas,
Kazimieras Černis and Mark Zalcik
Earth, Planets and Space 2014, 66:98 doi:10.1186/1880-5981-66-98
Received: 29 March 2014, Accepted: 16 August 2014, Published: 26 August 2014

AbstractLong-term systematic observations of noctilucent clouds in the regions of Moscow (Russia), Vilnius (Lithuania), and La Ronge(Canada) are considered. Variables, describing the seasonal activity of noctilucent clouds, are discussed. It is shown that there
are no statistically significant trends within time intervals of several recent decades. This result is compared to other known
findings on trends in mesospheric clouds. Based on the data of the modern ground-based noctilucent cloud observing
network in the northern hemisphere and simultaneous satellite data on mesospheric temperature and humidity, we estimate
sensitivity of noctilucent clouds to the relative humidity of the upper mesosphere.
Such an approach allows us to discuss possible changes of the upper-mesosphericarelative humidity, which are consistent with a zero secular trend in noctilucent cloud
activity.
30

NLC number

25
20
15
10
5

Keywords: Noctilucent clouds; Midlatitude mesosphere; Long-term trends;

0
1990

Relative NLC number

Mesospheric temperature; Mesospheric humidity

0.8

1992

b

1994

1996

1998

2000

2002

2004

2006

Y=(−0.001±0.009) (X−1990)+(−0.147±0.098) Ly +1.1
α

0.7

2008

o

2010

2012

2014

Relative NLC number
2−D regression model Y
Linear trend

0.6
0.5
0.4
0.3
0.2
0.1
1990

1992

1994

1996

1998

2000

2002

Years

2004

2006

2008

2010

2012

2014

Figure 1*Corresponding author: Nikolay Pertsev, n.pertsev@bk.ru

LETTER

Open AccessInfluence of DE3 tide on the equinoctial asymmetryof the zonal mean ionospheric electron density
Zhipeng Ren*, Weixing Wan, Jiangang Xiong and Libo Liu
Earth, Planets and Space 2014, 66:117 doi:10.1186/1880-5981-66-117
Received: 29 March 2014, Accepted: 4 September 2014, Published: 17 September 2014

Abstract
Through respectively adding September DE3 tide and March DE3 tide at the low boundary of Global Coupled IonosphereThermosphere-Electrodynamics Model, Institute of Geology and Geophysics, Chinese Academy of Sciences (GCITEM-IGGCAS),
we simulate the influence of DE3 tide on the equinoctial asymmetry of the zonal mean ionospheric electron density. The
influence of DE3 tide on the equinoctial asymmetry of the zonal mean electron density varies with latitude, altitude, and solar
activity level. Compared with the density driven by the September DE3 tide, the March DE3 tide mainly decreases the lower
ionospheric zonal mean electron density and mainly increases the electron density at higher ionosphere. In the low-latitude
ionosphere, DE3 tide drives an equatorial ionization anomaly (EIA) structure at higher ionosphere in the relative difference of
zonal mean electron density, which suggests that DE3 tide affects the longitudinal mean equatorial vertical E × B plasma drifts.
Although the lower ionospheric equinoctial asymmetry driven by DE3 tide mainly decreases with the increase of solar activity,
the asymmetry at higher ionosphere mainly increases with solar activity. However,EIA in equinoctial asymmetry mainly decreases with the increase of solar activity.

Keywords: Ionospheric equinoctial asymmetry; DE3 tide; Ionosphere-atmosphere
coupling

Figure 1*Corresponding author: Zhipeng Ren, zpren@mail.iggcas.ac.cn
20Earth, Planets and SpaceLETTER 

Open Access

Performance of the SciBar cosmic ray telescope (SciCRT) toward
the detection of high-energy solar neutrons in solar cycle 24
Yoshinori Sasai*, Yuya Nagai, Yoshitaka Itow, Yutaka Matsubara, Takashi Sako, Diego Lopez, Tsukasa Itow,
Kazuoki Munakata, Chihiro Kato, Masayoshi Kozai, Takahiro Miyazaki, Shoichi Shibata, Akitoshi Oshima,
Hiroshi Kojima, Harufumi Tsuchiya, Kyoko Watanabe, Tatsumi Koi, Jose Francisco Valdés-Galicia, Luis Xavier González,Ernesto Ortiz, Octavio Musalem, Alejandro Hurtado, Rocio Garcia and Marcos Anzorena
Earth, Planets and Space 2014, 66:130 doi:10.1186/1880-5981-66-130
Received: 2 May 2014, Accepted: 17 September 2014, Published: 30 September 2014

Abstract
We plan to observe solar neutrons at Mt. Sierra Negra (4,600 m above sea level) in Mexico using the SciBar detector. This project isnamed the SciBar Cosmic Ray Telescope (SciCRT). The main aims of the SciCRT project are to observe solar neutrons to study themechanism of ion acceleration on the surface of the sun and to monitor the anisotropy of galactic cosmic-ray muons. The SciBar
detector, a fully active tracker, is composed of 14,848 scintillator bars, whose dimension is
300 cm × 2.5 cm × 1.3 cm. The structure of the detector enables us to obtain the particle
trajectory and its total deposited energy. This information is useful for the energy
reconstruction of primary neutrons and particle identification. The total volume of thedetector is 3.0 m × 3.0 m × 1.7 m. Since this volume is much larger than the solar neutrontelescope (SNT) in Mexico, the detection efficiency of the SciCRT for neutrons is highly
enhanced. We performed the calibration of the SciCRT at Instituto Nacional de Astrofisica,
Optica y Electronica (INAOE) located at 2,150 m above sea level in Mexico in 2012. We
installed the SciCRT at Mt. Sierra Negra in April 2013 and calibrated this detector in May
and August 2013. We started continuous observation in March 2014. In this paper, we
report the detector performance as a solar neutron telescope and the current status of
the SciCRT.

Keywords: Cosmic-ray; Solar neutron; Scintillator bar

Figure 1*Corresponding author: Yoshinori Sasai, sasaiyoshinori@stelab.nagoya-u.ac.jp

LETTER 

Open Access

Relationship between the equatorial electrojet and global Sq currents
at the dip equator region
Nurul Shazana Abdul Hamid*, Huixin Liu*, Teiji Uozumi, Kiyohumi Yumoto, Bhaskara Veenadhari, Akimasa Yoshikawa
and Jairo Avendaño Sanchez
Earth, Planets and Space 2014, 66:146 doi:10.1186/s40623-014-0146-2
Received: 31 March 2014, Accepted: 16 October 2014, Published: 29 October 2014

Abstract
The equatorial electrojet (EEJ) is a strong eastward ionospheric current flowing in a narrow band along the dip equator. In thisstudy, we examined the EEJ-Sq relationship by using observations at six stations in the South American, Indian, and Southeast
Asian sectors. The analysis was carried out with data on geomagnetically quiet days with Kp ≤3 from 2005 to 2011. A
normalization approach was used because it yields more accurate results by overcoming the uncertainties due to latitudinalvariation of the EEJ and Sq. A weak positive correlation between the EEJ and Sq was obtained in the Southeast Asian sector,
while weak negative correlations were obtained in the South American and Indian sectors. EEJ-Sq relationship is found to be
independent of the hemispheric configuration of stations used to calculate their magnetic perturbations, and it also onlychanged slightly during low and moderate solar activity levels. These results demonstrate that the Southeast Asian sector isindeed different from the Indian and South American sectors, which is indicative of unique physical processes particularly
related to the electro-dynamo. Furthermore, we also demonstrate that the definition of the EEJ, that is, the total current orenhanced current, can significantly affect the conclusions drawn from EEJ-Sq correlations.

Keywords: H component; Equatorial electrojet; Sq current; Longitudinal
dependence

Figure 1*Corresponding authors: Nurul SA Hamid, shazana.ukm@gmail.com; Huixin Liu, huixin@serc.kyushu-u.ac.jp
21International CAWSES-II Symposium

LETTER

Open AccessStudy of plasma flow reversal in the near-Earth plasma sheet using
numerical computations
Koji Kondoh* and Tohru Shimizu
Earth, Planets and Space 2014, 66:147 doi:10.1186/s40623-014-0147-1
Received: 31 March 2014, Accepted: 15 August 2014, Published: 29 October 2014

Abstract
Tailward flow in the near-Earth plasma sheet associated with a rebound of the earthward bursty bulk flow (BBF) is investigatedusing three-dimensional magnetohydrodynamics simulations of magnetic reconnection in the magnetotail on the basis of
the spontaneous fast reconnection model. In order to investigate the properties of this tailward flow, virtual satellites arelocated at different positions in the plasma sheet within the simulation region, so that we can directly observe the temporalvariations of plasma quantities in accordance with the growth and preceding the flow reversal associated with the magnetic
reconnection. The time profile of the plasma flow velocity in the course of the BBF depends on the satellite position.
Furthermore, the time profile of the magnetic field strength in the course of the reverse flow depends on the satellite positionin the dawn-dusk direction. As a result of the rebound of the earthward flow, the accumulation of the plasma density and theplasma pressure is observed at any position in the plasma sheet during the interval
0.25
between the BBF and the reverse flow.

Keywords: Magnetic reconnection; Bursty bulk flow; Flow reversal; MHD simulation

0.2

0.15

0.1

0.05

0
20

25

30

35

40

45

50

55

Figure 1*Corresponding author: Koji Kondoh, kondo@cosmos.ehime-u.ac.jp

LETTER

Lidar returns from the upper atmosphere of Kamchatka
for 2008 to 2014 observations
Vasily V Bychkov*, Yuri А Nepomnyashchiy, Andrey S Perezhogin and Boris M Shevtsov
Earth, Planets and Space 2014, 66:150 doi:10.1186/s40623-014-0150-6
Received: 30 March 2014, Accepted: 29 October 2014, Published: 14 November 2014

Abstract
The correlation of lidar returns at a wavelength of 532 nm at altitudes of 150 to 300 km is investigated with the parameters of
the night ionospheric F2 layer. Moreover, the role of excited ions of the nitrogen atoms in the formation of lidar signals is
discussed.

Figure 1*Corresponding author: Vasily V Bychkov, vasily.v.bychkov@gmail.com
22

Earth, Planets and SpaceLETTER

Open Access

The spatial density gradient of galactic cosmic rays and its solar cycle
variation observed with the Global Muon Detector Network
Masayoshi Kozai*, Kazuoki Munakata, Chihiro Kato, Takao Kuwabara, John W Bieber, Paul Evenson,
Marlos Rockenbach, Alisson Dal Lago, Nelson J Schuch, Munetoshi Tokumaru, Marcus L Duldig, John E Humble,
Ismail Sabbah, Hala K Al Jassar, Madan M Sharma and Jozsef Kóta
Earth, Planets and Space 2014, 66:151 doi:10.1186/s40623-014-0151-5
Received: 31 March 2014, Accepted: 29 October 2014, Published: 14 November 2014

Abstract
We derive the long-term variation of the three-dimensional (3D) anisotropy of approximately 60 GV galactic cosmic rays (GCRs) from the data
observed with the Global Muon Detector Network (GMDN) on an hourly basis and compare it with the variation deduced from a conventional analysisof the data recorded by a single muon detector at Nagoya in Japan. The conventional analysis uses a north-south (NS) component responsive toslightly higher rigidity (approximately 80 GV) GCRs and an ecliptic component responsive to the same rigidity as the GMDN. In contrast, the GMDN
provides all components at the same rigidity simultaneously. It is confirmed that the temporal variations of the 3D anisotropy vectors including the
NS component derived from two analyses are fairly consistent with each other as far as the yearly mean value is concerned. We particularly compare
the NS anisotropies deduced from two analyses statistically by analyzing the distributions of the NS anisotropy on hourly and daily bases. It is foundthat the hourly mean NS anisotropy observed by Nagoya shows a larger spread than the daily mean due to the local time-dependent contribution
from the ecliptic anisotropy. The NS anisotropy derived from the GMDN, on the other hand, shows
similar distribution on both the daily and hourly bases, indicating that the NS anisotropy is
successfully observed by the GMDN, free from the contribution of the ecliptic anisotropy. By analyzing
the NS anisotropy deduced from neutron monitor (NM) data responding to lower rigidity(approximately 17 GV) GCRs, we qualitatively confirm the rigidity dependence of the NS anisotropy inwhich the GMDN has an intermediate rigidity response between NMs and Nagoya. From the 3D
anisotropy vector (corrected for the solar wind convection and the Compton-Getting effect arisingfrom the Earth’s orbital motion around the Sun), we deduce the variation of each modulation
parameter, i.e., the radial and latitudinal density gradients and the parallel mean free path for the
pitch angle scattering of GCRs in the turbulent interplanetary magnetic field. We show the derived
density gradient and mean free path varying with the solar activity and magnetic cycles.
Keywords: Diurnal anisotropy; North-south anisotropy; Heliospheric modulation of galactic
Figure 1
cosmic rays; Solar cycle variation of the cosmic ray density gradient*Corresponding author: Masayoshi Kozai, 13st303f@shinshu-u.ac.jp

LETTER

Open Access

Methods of analysis of geomagnetic field variations
and cosmic ray data
Oksana V Mandrikova*, Igor S Solovev and Timur L Zalyaev
Earth, Planets and Space 2014, 66:148 doi:10.1186/s40623-014-0148-0
Received: 31 March 2014, Accepted: 29 October 2014, Published: 21 November 2014

Abstract
In the present paper, we propose a wavelet-based method of describing variations in the Earth’s magnetic field, such as thehorizontal component of the geomagnetic field, in addition to methods for evaluating changes in the energy characteristicsof the field and for isolating the periods of increased geomagnetic activity. Based on a combination of multiresolution wavelet
decompositions with neural networks, we propose a method of approximation of the cosmic ray time course and theallocation of anomalous variations (Forbush effects) that occur during periods of high solar activity. During the realization of
the method, an algorithm was created for selecting the level of the wavelet decomposition and adaptive construction of theneural network. By using the proposed methods, we performed a joint analysis of the geomagnetic field and cosmic rays
during periods of strong magnetic storms. The strongest geomagnetic field perturbations were observed in periods ofabnormal changes in cosmic ray level. Assessment of the intensity of geomagnetic
disturbances on the eve of and during magnetic storm development allowed us tohighlight local increases in intensity of the geomagnetic field occurring at different
frequency ranges prior to the development of the storm’s main phase.
Implementation of the proposed method with theoretical tools in combination withother methods will improve the estimation accuracy of the geomagnetic field state
during space weather forecasting.

Keywords: Geomagnetic field; Cosmic rays; Wavelet transform; Neural networks;
Magnetic storms

Figure 1*Corresponding author: Oksana V Mandrikova, oksanam1@mail.ru
23

International CAWSES-II Symposium

LETTER

Open Access

Reaction of electric and meteorological states of the near-groundatmosphere during a geomagnetic storm on 5 April 2010
Sergey Smirnov
Earth, Planets and Space 2014, 66:154 doi:10.1186/s40623-014-0154-2
Received: 30 March 2014, Accepted: 8 November 2014, Published: 26 November 2014

Abstract
The effects of a geomagnetic storm on 5 April 2010 on electric parameters of theatmospheric near-ground layer in Kamchatka have been investigated. Three processes
over the course of the storm were identified. Air electroconductivity began to decrease
4 h before the storm, and this lasted for 20 h. The storm’s sudden commencement
caused potential gradient oscillations with amplitudes up to 300 V/m. During the stagesof the storm, a significant increase in the atmosphere ion content unipolarity coefficient
occurred.

Figure 1

Corresponding author: Sergey Smirnov, sergey@ikir.ru

LETTER

Open AccessApproaches for modeling ionosphere irregularities basedon the TEC rate index
Iurii Cherniak*, Irina Zakharenkova and Andrzej Krankowski
Earth, Planets and Space 2014, 66:165 doi:10.1186/s40623-014-0165-z
Received: 30 April 2014, Accepted: 30 November 2014, Published: 12 December 2014

Abstract
The ionosphere plays an important role in GNSS applications because it influences radio wave propagation. The ionosphericdelay is the biggest error source for satellite navigation signals, but it can be directly measured and mitigated using dualfrequency GNSS receivers. However, the GNSS signal fades because of electron density gradients and irregularities in theionosphere, decreasing the operational performance of navigation systems. Recently, several models were developed toreproduce the ionospheric fluctuations and scintillation activity under different
geophysical conditions, but these models were calibrated with data sets without GNSSderived experimental total electron content (TEC) data. There is a great demand for aproper model of ionospheric irregularity specification based on GNSS TEC
measurements. In this work, we use data from the permanent GNSS network to develop
the empirical model of the ionospheric irregularities over the Northern Hemisphere. As
initial data, we used the daily dependences of the rate of TEC index (ROTI) as a functionof geomagnetic local time on the specific grid. The ROTI maps allow us to estimate theoverall fluctuation activity and the auroral oval evolution. The irregularities of thesouthern oval border were determined with the ROTI. This paper presents thecorrelation between the Kp geomagnetic index and parameters that characterized theactivity of the ionosphere irregularities in 2010 to 2013.
Keywords: Ionosphere; TEC fluctuations; Irregularities oval; Empirical model; Space
weather*Corresponding author: Iurii Cherniak, tcherniak@ukr.net
24

Figure 1

Earth, Planets and SpaceLETTER

Open Access

High-midlatitude ionosphere response to major stratosphericwarming
Boris G Shpynev*, Vladimir I Kurkin, Konstantin G Ratovsky, Marina A Chernigovskaya, Anastasiya Yu Belinskaya,
Svetlana A Grigorieva, Alexander E Stepanov, Vasily V Bychkov, Dora Pancheva and Plamen Mukhtarov
Earth, Planets and Space 2015, 67:18 doi:10.1186/s40623-015-0187-1
Received: 28 April 2014, Accepted: 15 January 2015, Published: 11 February 2015

Abstract
This study investigates the impact of dynamical processes in the neutral atmosphere on the high-midlatitude ionosphere during two
sudden stratospheric warming (SSW) events. For this purpose, the reanalysis meteorological data of the National Centers forEnvironmental Prediction/National Center for Atmospheric Research (NCEP/NCAR) and UK Met Office (UKMO) were used in addition
to that from the high-midlatitude chain of Russian ionosonde stations. The results show that the ionospheric response to the SSW
events at high-midlatitudes depends on the position of the ionosonde stations relative to the stratospheric circulation pattern. Twowell-pronounced effects were detected in this study. The first effect, observed in January 2009, was a negative effect in criticalfrequency (foF2) and a positive effect in F2 layer maximum (hmF2) above the border of a stratospheric cyclone and an anticyclone withnorthward flow direction. During a 6-day period, the ionosphere exhibited a sharply inhomogeneous longitudinal structure whenionosondes, displaced at a longitude of approximately 20°, showed differences of approximately 1 MHz in foF2 and more than 50 km
in hmF2. The second feature, which was clearly observed in January 2013, implied apositive effect in foF2 up to approximately 2.5 MHz and a negative effect in hmF2 atapproximately 10 km above the center of the stratospheric cyclone. We conclude thatthese effects were caused by upward transport of molecular gas to the lower
thermosphere for the first case and a pulldown forcing of molecular species above thelow-pressure zone inside the cyclone for the second case. Changes in the O+/N2 ratio in
the lower thermosphere altered the O+ recombination rate and the corresponding
variations of ionosphere parameters.

Keywords: Sudden stratospheric warming; Atmosphere-ionosphere coupling;
Ground-based ionosonde measurements

Figure 1*Corresponding author: Boris G Shpynev, shpynev@iszf.irk.ru

LETTER

Open Access

Statistical study of medium-scale traveling ionospheric disturbances
using SuperDARN Hokkaido ground backscatter data for 2011
Alexey V Oinats*, Vladimir I Kurkin and Nozomu Nishitani
Earth, Planets and Space 2015, 67:22 doi:10.1186/s40623-015-0192-4
Received: 30 April 2014, Accepted: 23 January 2015, Published: 15 February 2015

Abstract
We describe an automated technique to determine parameters of traveling ionospheric disturbances (TIDs) using the Super
Dual Auroral Radar Network (SuperDARN) high frequency (HF) radar data. The technique is based on the analysis of minimum
ground backscatter range variations corresponding to different radar beams. Using this technique, we processed theSuperDARN Hokkaido radar data for 2011 and revealed statistical distributions of medium-scale TID (MSTID) azimuth andapparent horizontal velocity. We found four peaks with a distinct diurnal and seasonal dependence in the MSTID azimuth
occurrence rate distributions. Northeast MSTID azimuths (20° to 50°) are typical of the summer and equinox morning hours;
southeast azimuths (100° to 140°) prevail in the winter daytime; southwest azimuths (190° to 220°) are typical mostly in thesummer and equinox nighttime and in the equinox evening; northwest azimuths (280° to 320°) are typical of the summer
daytime and evening. The apparent horizontal velocities are generally within the 100
to 160 m/s range. The obtained results agree well with earlier studies by otherresearchers. However, there are also certain differences. The summer daytime
northwestward MSTIDs are not indicated in the earlier studies. The nighttime
horizontal velocities are 1.5 to 2 times higher than those in the daytime.
Furthermore, winter velocity values are about 1.5 times higher than those in otherseasons. These differences might be associated with the peculiarities of the data
recorded by different facilities, or the features of the processing techniques, andrequire further investigation for their interpretation.

Keywords: Medium-scale traveling ionospheric disturbances; Atmospheric gravity
waves; SuperDARN Hokkaido radar

Figure 1*Corresponding author: Alexey V Oinats, oinats@iszf.irk.ru
25

International CAWSES-II Symposium

LETTER

Open AccessRegional climate pattern during two millennia estimated fromannual tree rings of Yaku cedar trees: a hint for solar variability?
Yasushi Muraki*, Takumi Mitsutani, Shoichi Shibata, Syuichi Kuramata, Kimiaki Masuda and Kentaro Nagaya
Earth, Planets and Space 2015, 67:31 doi:10.1186/s40623-015-0198-y
Received: 1 April 2014, Accepted: 27 January 2015, Published: 27 February 2015

Abstract
We analyzed trees that have survived on Yaku island (Yakushima) for 2,000 years. Quite surprisingly, the Fourier and wavelet
analyses of the annual growth rate identified 2 cycles of periodicities of 11 and (24 ± 4) years during the Oort, Wolf, Spörer,Maunder, and Dalton minima. The 11-year periodicity originated from solar activity, while the (24 ± 4)-year periodicity may berelated to the Pacific Decadal Oscillation (PDO). In particular, we have discovered an 11-year periodicity in the meteorological
daylight-hour data from Yakushima in the month of June during 1938 to 2013 and a 24-year periodicity in July. The growthrate of the tree rings may be affected by the variation of the daylight hour.

Keywords: Sun-earth relation; Tree rings; Grand minima; Dendrochronology; Climate change

Figure 1*Corresponding author: Yasushi Muraki, muraki@stelab.nagoya-u.ac.jp

LETTER

Open AccessSearch for solar neutrons at Mount Chacaltaya associated with
M- and X-class flares during the rising period of solar cycle 24
Diego Lopez* and Yutaka Matsubara
Earth, Planets and Space 2015, 67:54 doi:10.1186/s40623-015-0222-2
Received: 2 May 2014, Accepted: 30 March 2015, Published: 23 April 2015

Abstract
To better understand the acceleration mechanism of high-energy particles that are driven by solar flares, we examined solar
neutron signals. We have performed a statistical analysis by reviewing the data collected by a neutron monitor during theperiod of January 2010 to August 2013. This detector operates at Mount Chacaltaya in Bolivia at 5,200 m above sea level. Our
aim is to search for solar neutron events in association with large solar flares observed by the GOES satellite. We report that
our analysis did not yield any positive excess due to solar neutrons that are statistically significant. Hence, we calculated theupper limit of the number of solar neutrons for the X2.8-class solar flare which occurred on 13 May 2013. We performed asimilar calculation with a solar neutron event that occurred on 7 September 2005. Our upper limit is seven times less than the
one produced by the real signal.

Keywords: Solar neutrons; Neutron monitor

Figure 1*Corresponding author: Diego Lopez, ndlopez@stelab.nagoya-u.ac.jp
26Earth, Planets and SpaceTECHNICAL REPORT

Open Access

Progress of the IUGONET system - metadata databasefor upper atmosphere ground-based observation data
Shuji Abe*, Norio Umemura, Yukinobu Koyama, Yoshimasa Tanaka, Manabu Yagi, Akiyo Yatagai, Atsuki Shinbori,
Satoru UeNo, Yuka Sato and Naoki Kaneda
Earth, Planets and Space 2014, 66:133 doi:10.1186/1880-5981-66-133
Received: 31 March 2014, Accepted: 24 September 2014, Published: 14 October 2014

Abstract
Background: The Interuniversity Upper atmosphere Global Observation NETwork (IUGONET) project is a 6-year research
project which started in 2009. The objective of this project is to establish a metadata database of various ground-based
observation data covering a wide region from the Sun to the Earth; this will encourage more studies on the mechanisms oflong-term variations in the upper atmosphere.
Findings: For archiving purposes, the metadata database system for cross-searching various data distributed across many
universities and institute was developed based on the existing repository software called DSpace as the core component andthe Space Physics Archive Search and Extract (SPASE) data model as the metadata format. The IUGONET metadata database isstill in operation since it was released in March 2012. The system is continuously examined, tested, and updated to improve its
quality. The OpenSearch interface in the IUGONET metadata database allows the user to use external applications easily forexchanging metadata and/or for analyzing data.
Conclusions: We conducted self-examination of our product, which was added forplanning future directions of the IUGONET project.

Keywords: Metadata database; Analysis software; Upper atmospheric physics; Earthand planetary sciences; Ground-based observation

Figure 1*Corresponding author: Shuji Abe, abeshu@icswse.kyushu-u.ac.jp

TECHNICAL REPORT

Open Access

The capacity-building and science-enabling activities of the IUGONET
for the solar-terrestrial research community
Akiyo Yatagai*, Yuka Sato, Atsuki Shinbori, Shuji Abe, Satoru UeNo and IUGONET project team
Earth, Planets and Space 2015, 67:2 doi:10.1186/s40623-014-0170-2
Received: 15 November 2014, Accepted: 10 December 2014, Published: 8 January 2015

Abstract
Background: This paper presents an overview of the capacity-building activities and science-enabling services of the Inter-university Upper
atmosphere Global Observation NETwork (IUGONET) project. This Japanese program, which started in 2009, is building a metadata database(MDDB) of ground-based observations and is developing an analysis software to handle the data linked to the MDDB system for use by thesolar-terrestrial physics community. Because the institutional members of the IUGONET are mainly universities in Japan, we explore tools thatcan contribute to advanced education as well as promote research activities.
Findings: In this paper, we describe the utilities of the IUGONET for education, including our capacity-building activities in developing
countries. We have regularly facilitated training seminars for Japanese students on the use of our tools (IUGONET MDDB and the software),and we have held capacity-building seminars for young scientists in developing countries. In addition to the MDDB, we have prepared various‘gateway’ tools for users who are unfamiliar with ‘keywords’ to search for data. One of these is a geographical display tool that uses Google
Earth (KML file), which is included as supplemental material to this paper. The usefulness of the
IUGONET has been proven over its first 5 years of operation by the increasing number of its
users, which has led to the production of approximately 500 scientific papers, including 42
thesis papers.
Conclusions: The IUGONET community collaborates with the Scientific Committee on SolarTerrestrial Physics program, not only in its scientific activities, but also in the establishment of
E-infrastructure and capacity building.

Keywords: Ground-based observation; Solar-terrestrial physics (STP); Database;

Metadata; Interdisciplinary studies; Capacity building; E-infrastructure*Corresponding author: Akiyo Yatagai, akiyoyatagai@stelab.nagoya-u.ac.jp
27

Figure 1

Information for Contributors
General1.

Manuscripts should be submitted through the journal’s Editorial Manager system(https://www.editorialmanager.com/epsp/default.aspx).

2.

Only papers not previously published will be accepted, and the emphasis is on theoriginality of concept or observation.

3.

Four varieties of article types are available.
3.1“Full papers” without word limit.

3.2“Letters” have a limit of 11,000 words including legends for figures and tables. One
figure or table not exceeding one A4 page is counted as 500 words.

4.

3.3

“Frontier Letters” can be submitted upon invitation by the Editor-in-Chief.

3.4“Technical reports” describe the technical development of instrument or software.

Authors retain the copyright, and distribution of articles is free under cc-by license.

Technical
1.

Manuscripts should be written in English with double spacing.

2.

Each manuscript should be organized in the following order: title, authors’ names,
affiliations, abstract, key words, main text, acknowledgement, appendix, references, andsupplementary materials.

3.

The corresponding author should be clearly indicated.

4.

The abstract is limited to 300 words and should be informative and include principal
findings and conclusions. Please avoid abbreviations.

5.

The main text can have multiple free headings.

6.

High-resolution figures should be provided in the following format; PDF (preferred
format for diagrams), PNG (preferred format for photos or images), EPS ,TIFF, JPEG, BMP.

7.

References must follow the Springer Basic style.

Correspondence
If you have any questions, please contact editorial@earth-planets-space.com.

© EPS Steering Committee 2016 All rights reserved.
A Grant-in-Aid for Publication of Scientific Research Results (251001) from Japan
Society for the Promotion of Science is used for printing.

Continued from back cover

The spatial density gradient of galactic cosmic rays and its solar cycle variation observed with the Global Muon
Detector Network . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Masayoshi Kozai, Kazuoki Munakata, Chihiro Kato, Takao Kuwabara, John W Bieber,Paul Evenson, Marlos Rockenbach, Alisson Dal Lago, Nelson J Schuch, Munetoshi Tokumaru,
Marcus L Duldig, John E Humble, Ismail Sabbah, Hala K Al Jassar, Madan M Sharma and Jozsef Kóta  23

Methods of analysis of geomagnetic field variations and cosmic ray data
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  Oksana V Mandrikova, Igor S Solovev and Timur L Zalyaev  23
Reaction of electric and meteorological states of the near-ground atmosphere during a geomagnetic storm on 5 April
2010 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Sergey Smirnov   24Approaches for modeling ionosphere irregularities based on the TEC rate index. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  Iurii Cherniak, Irina Zakharenkova and Andrzej Krankowski  24
High-midlatitude ionosphere response to major stratospheric warming. . . . . . . . . . . . . . . . . . . . .  Boris G Shpynev, Vladimir I Kurkin, Konstantin G Ratovsky, Marina A Chernigovskaya, Anastasiya Yu Belinskaya,

Svetlana A Grigorieva, Alexander E Stepanov, Vasily V Bychkov, Dora Pancheva and Plamen Mukhtarov  25

Statistical study of medium-scale traveling ionospheric disturbances using SuperDARN Hokkaido ground backscatterdata for 2011 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Alexey V Oinats, Vladimir I Kurkin and Nozomu Nishitani  25
Regional climate pattern during two millennia estimated from annual tree rings of Yaku cedar trees: a hint for solar
variability? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Yasushi Muraki, Takumi Mitsutani, Shoichi Shibata, Syuichi Kuramata,Kimiaki Masuda and Kentaro Nagaya  26

Search for solar neutrons at Mount Chacaltaya associated with M- and X-class flares during the rising period of solar
cycle 24 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Diego Lopez and Yutaka Matsubara  26
Progress of the IUGONET system - metadata database for upper atmosphere ground-based observation data
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  Shuji Abe, Norio Umemura, Yukinobu Koyama, Yoshimasa Tanaka, Manabu Yagi, Akiyo Yatagai,

Atsuki Shinbori, Satoru UeNo, Yuka Sato and Naoki Kaneda  27

The capacity-building and science-enabling activities of the IUGONET for the solar-terrestrial research community. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Akiyo Yatagai, Yuka Sato, Atsuki Shinbori, Shuji Abe, Satoru UeNo and IUGONET project team  27

Cover image: Iwai, K. et al., Earth, Planets and Space 2014, 66:149 doi:10.1186/s40623-014-0149-z

Contents
Special issue “International CAWSES-II Symposium”. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Mamoru Yamamoto, Kazuo Shiokawa, Takuji Nakamura and Nat Gopalswamy
Correlation between the global occurrences of ionospheric irregularities and deep atmospheric convective clouds inthe intertropical convergence zone (ITCZ) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Shin-Yi Su, Chung Lung Wu and Chao Han Liu
Coronal magnetic field and the plasma beta determined from radio and multiple satellite observations. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Kazumasa Iwai, Kiyoto Shibasaki, Satoshi Nozawa, Takuya Takahashi, Shinpei Sawada,
Jun Kitagawa, Shun Miyawaki and Hirotaka Kashiwagi

High-latitude GPS phase scintillation and cycle slips during high-speed solar wind streams and interplanetary coronalmass ejections: a superposed epoch analysis . . . . . . Paul Prikryl, P Thayyil Jayachandran, Sajan C Mushini and Ian G Richardson
Space weather effects on the low latitude D-region ionosphere during solar minimum. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Abhikesh Kumar and Sushil Kumar
Global distribution of the migrating terdiurnal tide seen in sporadic E occurrence frequencies obtained from GPS radio
occultations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Tilo Fytterer, Christina Arras, Peter Hoffmann and Christoph Jacobi
Vertical coupling of atmospheres: dependence on strength of sudden stratospheric warming and solar activity. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Fazlul I Laskar, Duggirala Pallamraju and Bhaskara Veenadhari
Empirical modeling of the storm time geomagnetic indices: a comparison between the local K and global Kp indices. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Jean Uwamahoro and John Bosco Habarulema
Climatology of the diurnal tides from eCMAM30 (1979 to 2010) and its comparison with SABER. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Quan Gan, Jian Du, William E Ward, Stephen R Beagley, Victor I Fomichev and Shaodong Zhang
Major solar eruptions and high-energy particle events during solar cycle 24. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Nat Gopalswamy, Hong Xie, Sachiko Akiyama, Pertti A Mäkelä and Seiji Yashiro
Effect of solar cycle 23 in foF2 trend estimation . . . . . . . . . . . Ana G Elias, Blas F de Haro Barbas, Kiyoto Shibasaki and Jonas R Souza
Filtering ionosphere parameters to detect trends linked to anthropogenic effects . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Ana G Elias
New perspectives on thermosphere tides: 2. Penetration to the upper thermosphere. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Jeffrey M Forbes, Xiaoli Zhang and Sean L Bruinsma
A long-term trend in the F2-layer critical frequency as observed at Alma-Ata ionosonde station. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Galina I Gordiyenko, Victor V Vodyannikov, Artur F Yakovets and Yuriy G Litvinov
Study of Pc1 pearl structures observed at multi-point ground stations in Russia, Japan, and Canada. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Chae-Woo Jun, Kazuo Shiokawa, Martin Connors, Ian Schofield, Igor Poddelsky and Boris Shevtsov
New perspectives on thermosphere tides: 1. Lower thermosphere spectra and seasonal-latitudinal structures. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Alexander O Truskowski, Jeffrey M Forbes, Xiaoli Zhang and Scott E Palo
A statistical study of satellite traces and evolution of equatorial spread F. . . . . . . . . . . . . . . . . . . . . . . . . . . . Viswanathan Lakshmi Narayanan, Sukanta Sau, Subramanian Gurubaran, Kazuo Shiokawa, Nanan Balan,Kaliappan Emperumal and Samireddipalle Sripathi

1
9

9
10
10
11
11
12
12
13
13
14
14
15
15
16

16

Long-term variation in the upper atmosphere as seen in the geomagnetic solar quiet daily variation. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Atsuki Shinbori, Yukinobu Koyama, Masahito Nose, Tomoaki Hori, Yuichi Otsuka and Akiyo Yatagai 17
Fast and ultrafast Kelvin wave modulations of the equatorial evening F region vertical drift and spread F development. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Mangalathayil A Abdu, Christiano GM Brum, Paulo P Batista, Subramanian Gurubaran, Dora Pancheva,
Jose V Bageston, Inez S Batista and Hisao Takahashi

Polarization analysis of VLF/ELF waves observed at subauroral latitudes during the VLF-CHAIN campaign. . . . . . . . . . . . . . . Claudia Martinez-Calderon, Kazuo Shiokawa, Yoshizumi Miyoshi, Mitsunori Ozaki, Ian Schofield and Martin Connors
Airglow-imaging observation of plasma bubble disappearance at geomagnetically conjugate points. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Kazuo Shiokawa, Yuichi Otsuka, Kenneth JW Lynn, Philip Wilkinson and Takuya Tsugawa
Effects of pre-reversal enhancement of E × B drift on the latitudinal extension of plasma bubble in Southeast Asia
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Prayitno Abadi, Yuichi Otsuka and Takuya Tsugawa
Three-dimensional numerical simulation of nonlinear acoustic-gravity wave propagation from the troposphere to thethermosphere . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Nikolai M Gavrilov and Sergey P Kshevetskii
Noctilucent clouds observed from the ground: sensitivity to mesospheric parameters and long-term time series. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Nikolay Pertsev, Peter Dalin, Vladimir Perminov, Vitaly Romejko, Audrius Dubietis,
Ričardas Balčiunas, Kazimieras Černis and Mark Zalcik

17

18
18
19
19

20

Influence of DE3 tide on the equinoctial asymmetry of the zonal mean ionospheric electron density. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Zhipeng Ren, Weixing Wan, Jiangang Xiong and Libo Liu 20
Performance of the SciBar cosmic ray telescope (SciCRT) toward the detection of high-energy solar neutrons insolar cycle 24 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Yoshinori Sasai, Yuya Nagai, Yoshitaka Itow, Yutaka Matsubara, Takashi Sako, Diego Lopez,
Tsukasa Itow, Kazuoki Munakata, Chihiro Kato, Masayoshi Kozai, Takahiro Miyazaki, Shoichi Shibata, Akitoshi Oshima,
Hiroshi Kojima, Harufumi Tsuchiya, Kyoko Watanabe, Tatsumi Koi, Jose Francisco Valdés-Galicia, Luis Xavier González,Ernesto Ortiz, Octavio Musalem, Alejandro Hurtado, Rocio Garcia and Marcos Anzorena

Relationship between the equatorial electrojet and global Sq currents at the dip equator region. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Nurul Shazana Abdul Hamid, Huixin Liu, Teiji Uozumi, Kiyohumi Yumoto,
Bhaskara Veenadhari, Akimasa Yoshikawa and Jairo Avendaño Sanchez

Study of plasma flow reversal in the near-Earth plasma sheet using numerical computations. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Koji Kondoh and Tohru Shimizu
Lidar returns from the upper atmosphere of Kamchatka for 2008 to 2014 observations. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Vasily V Bychkov, Yuri А Nepomnyashchiy, Andrey S Perezhogin and Boris M Shevtsov
Continued on inside back cover

21

21
22
22