Coupling of the High and Mid Latitude Ionosphere and Its Relation to Geospace Dynamics

14:20 UT

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

Vice Editors-in-Chief
Masato Furuya, Hokkaido University, Japan
Solid Earth Science

Nozomu Nishitani, Nagoya University, Japan
Space Science

Editors
Yosuke Aoki
Nanan Balan
Stephen Bannister
Shanaka de Silva
Koji Fukuma
Lin-Ni Hau
Hauke Hussmann
Attila Komjathy
Alexey Kuvshinov

Huixin Liu
Takuto Maeda
Koji Matsumoto
Mitsuhiro Nakagawa
Junichi Nakajima
Yasuhiro Nariyuki
Azusa Nishizawa
Keiji Ohtsuki
Taku Ozawa

Takeshi Sakanoi
Martha K. Savage
Benoit Taisne
Hiroshi Takenaka
Hiroaki Toh
Yih-Min Wu
Akimasa Yoshikawa

Hiroo Kanamori
Jun'ichiro Kawaguchi
Takafumi Matsui
Hitoshi Mizutani

Toshitaka Tsuda
Zhongliang Wu
Kiyoshi Yomogida

Advisory Board
Benjamin Fong Chao
Bernard Chouet
Yoshimori Honkura
Toshihiko Iyemori

Journal Scope
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Earth, Planets and Space
Nishitani et al. Earth, Planets and Space (2016) 68:168
DOI 10.1186/s40623-016-0543-9

Open Access

PREFACESpecial issue “Coupling of the highand mid latitude ionosphere and its relation
to geospace dynamics”
Nozomu Nishitani1*, Tsutomu Nagatsuma2, Akira Sessai Yukimatu3, Hongqiao Hu4 and Takeshi Sakanoi5
The inductive effects of the magnetosphere during thecourse of a substorm have been studied by Mishin et al.
(2015).
Magnetosphere–ionosphere interaction, equatorwardof the auroral emission region (subauroral latitudes),often generates subauroral polarization streams (SAPS).
Nagano et al. (2015) have identified the slowest speed
limit of SAPS and have suggested that the ionospheric
feedback mechanism does not play a significant role inthe slower part of the SAPS.
The ionosphere is formed as a result of solar emission, magnetosphere–ionosphere coupling, and ionosphere–thermosphere coupling processes. It is important
to know the distribution of ionospheric plasma densities
in order to understand the formation processes of theionosphere. The characteristics of the distribution of ionospheric plasma density were studied by employing FORMOSAT-3/COSMIC satellite data (Chang et al. 2015),
GPS TEC data (Kumar et al. 2015), and SuperDARN HF
radar data (Oinats et al. 2016a). The results of the analysis of the observation data were compared with HWM93
simulation or International Reference Ionosphere (IRI)2012 model.
Additionally, the ionosphere is disturbed by ionospheric plasma instability processes and ionospheric–thermosphere coupling processes. The characteristicsof traveling ionospheric disturbances of various origins
were studied by employing SuperDARN HF radar data
(Oinats et al. 2016b). Tsunami-driven traveling ionospheric disturbances were studied by employing GPS
TEC data (Tang et al. 2015). Seif et al. (2015) have studied
the detailed characteristics of daytime ionospheric scintillation near the magnetic equator and have discussed
the role of gradient-drift instability in generating ionospheric plasma irregularities.
In addition, in order to study ionospheric characteristics, it is important to develop techniques to enhance the

The EPS special issue, Coupling of the High and Mid Latitude Ionosphere and Its Relation to Geospace Dynamics,
originated from a session held during the Asia Oceania
Geosciences Society (AOGS) 2014 meeting in Sapporo(Japan). In addition to the papers presented at the conference, others of common scientific interest have been
included. In the end, 12 papers have been published, covering a wide variety of scientific topics.
The focus of this special issue is on the coupling of
the high and mid latitude ionosphere, which plays animportant role in geospace dynamics. Recently, the coverage offered by ground-based observation networks,
such as magnetometers, high-frequency (HF) radars,
Global Positioning System (GPS) receivers and others,
has increased dramatically, improving our understandingof the coupling between the high and mid latitude ionosphere. In addition, several satellites in geospace provide
essential in situ data, yielding numerous new findings,
as well as posing new questions. The papers in this issue
contribute to our understanding of the high/mid (andlow/equatorial) latitude ionosphere and geospace coupling, as well as geospace dynamics.
Sudden changes in the dynamic pressure of solar wind,known as sudden impulses (SI), have a major influenceon the magnetosphere and ionosphere. Specifically, theSI have a significant effect on ionospheric convection athigh and mid latitudes, as observed by the Super Dual
Auroral Radar Network (SuperDARN) HF radars (Horiet al. 2015), as well as on auroral emissions (Liu et al.
2015). In addition, the interaction between solar wind
and the magnetosphere leads to substorms, which are
manifestations of the explosive energy release processes.
*Correspondence: nisitani@isee.nagoya‑u.ac.jp1
Institute for Space‑Earth Environmental Research, Nagoya University,
Nagoya, Japan
Full list of author information is available at the end of the article© 2016 The Author(s). 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, and reproduction 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

Coupling of the High and Mid Latitude Ionosphere and Its Relation to Geospace Dynamics
Nishitani et al. Earth, Planets and Space (2016) 68:168

Page 2 of 2

precision of analyzing observational data. Ponomarenko
et al. (2015) have developed an algorithm for calibrating
the elevation angle parameter of the SuperDARN radars,
which is important in identifying echo locations. Furthermore, it is important to model the ionospheric parameters to extract the main characteristics of ionosphericdisturbances. Mandrikova et al. (2015) have developed
an algorithm for modeling ionospheric parameter FoF2
and extracting the main characteristics of ionosphericperturbations during different seasons and geomagnetic
activities.
With the advance of observational techniques and the
expansion of the field of view of the existing observation network, as well as the development of modeling/
numerical simulation algorithms, we hope to enhance theunderstanding of the ionosphere, ranging from the highto mid/low latitude, and its relation to the dynamics ofthe geospace and upper atmosphere.

Hori T, Shinbori A, Fujita S, Nishitani N (2015) IMF‑By dependence of transient
ionospheric flow perturbation associated with sudden impulses: superD‑
ARN observations. Earth Planets Space 67:190
Kumar S, Tan EL, Murti DS (2015) Impacts of solar activity on performance of
the IRI‑2012 model predictions from low to mid latitudes. Earth Planets
Space 67:42
Liu J, Hu H, Han D, Yang H, Lester M (2015) Simultaneous ground‑based opticaland SuperDARN observations of the shock aurora at MLT noon. Earth
Planets Space 67:120
Mandrikova OV, Fetisova NV, Polozov YA, Solovev IS, Kupriyanov MS (2015)
Method for modeling of the components of ionospheric parameter time
variations and detection of anomalies in the ionosphere. Earth Planets
Space 67:131
Mishin VV, Mishin VM, Lunyushkin SB, Pu Z, Wang C (2015) Strong induction
effects during the substorm on 27 August 2001. Earth Planets Space
67:162
Nagano H, Nishitani N, Hori T (2015) Occurrence characteristics and lowest
speed limit of subauroral polarization stream (SAPS) observed by theSuperDARN Hokkaido East radar. Earth Planets Space 67:126
Oinats AV, Nishitani N, Ponomarenko P, Ratovsky KG (2016a) Diurnal andseasonal behavior of the Hokkaido East SuperDARN ground backscatter:
simulation and observation. Earth Planets Space 68:18
Oinats AV, Nishitani N, Ponomarenko P, Berngardt OI, Ratovsky KG (2016b)
Statistical characteristics of medium‑scale traveling ionospheric distur‑bances revealed from the Hokkaido East and Ekaterinburg HF radar data.
Earth Planets Space 68:8
Ponomarenko P, Nishitani N, Oinats AV, Tsuya T, St.‑Maurice J‑P (2015) Applica‑tion of ground scatter returns for calibration of HF interferometry data.
Earth Planets Space 67:138
Seif A, Tsunoda RT, Abdullah M, Hasbi AM (2015) Daytime gigahertz scintilla‑tions near magnetic equator: relationship to blanketing sporadic E andgradient‑drift instability. Earth Planets Space 67:177
Tang L, Zhang X, Li Z (2015) Observation of ionospheric disturbances inducedby the 2011 Tohoku tsunami using far‑field GPS data in Hawaii. Earth
Planets Space 67:88

Author details
1
Institute for Space‑Earth Environmental Research, Nagoya University, Nagoya,Japan. 2 National Institute of Information and Communications Technology,
Koganei, Japan. 3 National Institute of Polar Research, Tachikawa, Japan. 4 Polar
Research Institute of China, Shanghai, China. 5 Tohoku University, Sendai,
Japan.
Received: 6 October 2016 Accepted: 6 October 2016

References
Chang FY, Liu JY, Chang LC, Lin CH, Chen CH (2015) Three‑dimensional elec‑tron density along the WSA and MSNA latitudes probed by FORMOSAT‑3/
COSMIC. Earth Planets Space 67:156

2

Earth, Planets and SpaceFRONTIER LETTER Open Access

IMF-By dependence of transient ionospheric flow perturbation
associated with sudden impulses: SuperDARN observations
Tomoaki Hori*, Atsuki Shinbori, Shigeru Fujita and Nozomu Nishitani
Earth, Planets and Space 2015, 67:190 DOI: 10.1186/s40623-015-0360-6
Received: 31 March 2015, Accepted: 19 November 2015, Published: 25 November 2015

Abstract
A statistical study using a large dataset of Super Dual Auroral Radar Network (SuperDARN) observations is conducted fortransient ionospheric plasma flows associated with sudden impulses (SI) recorded on ground magnetic field. The global
structure of twin vortex-like ionospheric flows is found to be consistent with the twin vortices of ionospheric Hall current
deduced by the past geomagnetic field observations. An interesting feature, which is focused on in this study, is that the flow
structures show a dawn-dusk asymmetry depending on the combination of the polarity of SI and interplanetary magnetic
field (IMF)-By. Detailed statistics of the SuperDARN observations reveal that the dawn-dusk asymmetry of flow vortices due to
IMF-By appears during negative SIs, while such asymmetric characteristics are not seen during positive SIs. On the basis of the
upstream observations, we suggest that this particular dawn-dusk asymmetry is caused by the interaction between the
pre-existing round convection cell and a pair of the transient convection vortices associated with SIs.

Keywords: Sudden impulse; Ionospheric plasma convection;
SuperDARN

ts - 4mints -10min

Trise

s

SYM-H

negative SItpositive SI

Tpre-SI

Tpeak-SI

time

Figure 1*Corresponding author: Tomoaki Hori, tomo.hori@nagoya-u.jp

FULL PAPER

Open Access

Impacts of solar activity on performance of the IRI-2012
model predictions from low to mid latitudes
Sanjay Kumar*, Eng Leong Tan and Dhimas Sentanu Murti
Earth, Planets and Space 2015, 67:42 DOI: 10.1186/s40623-015-0205-3
Received: 9 September 2014, Accepted: 10 February 2015, Published: 21 March 2015

Abstract
This study investigates the impacts of solar activity on the performance of the latest release of International Reference Ionosphere (IRI) modelversion 2012 (IRI-2012) predictions during the ascending phase of solar activity from 2009 to 2013. The study is based on the data of total
electron content (TEC) retrieved from the Global Positioning System (GPS) at Singapore (NTUS) (geographic latitude 01.34°N, longitude
103.67°E, geomagnetic latitude 8.4°S), Thailand (CUSV) (geographic latitude 13.73°N, longitude 100.54°E, geomagnetic latitude 3.96°N), China(KUNM) (geographic latitude 25.02°N, longitude 102.79°E, geomagnetic latitude 15.15°N), Mongolia (ULAB) (geographic latitude 47.67°N,
longitude 107.05°E, geomagnetic latitude 37.73°S), and Russia (IRKM) (geographic latitude 52.21°N, 104.31°E, geomagnetic latitude 42.28°S).
The GPS-TEC has been compared with the IRI-2012 model TEC for three different options, namely, IRI-NeQ, IRI01-corr, and IRI-2001, for topside
Ne over all the above five stations lying at different latitudes from equatorial-equatorial
ionization anomaly (EIA) to mid-latitude regions but at around the same longitude line
(104° ± 3°E). The study showed that the IRI model predictions for different topside options aredifferent and significant in low-latitude region but insignificant in mid-latitude regions (except
during winter season of high solar activity year 2012). During the period from 2009 to 2013,
upon moving from low to high solar activity, the prediction nature (overestimation/
underestimation) of IRI-2012 model changes significantly at EIA station KUNM of low-latitude
region. The discrepancy in IRI-2012 model TEC as compared to GPS-TEC in low-latitude region isfound to be larger and significant than in mid-latitude region (Mongolia and Russia). The
discrepancy in the IRI-2012 model TEC with IRI-2001 topside is found to be maximum atequatorial station CUSV (RMSD 99%) during the solar minimum year 2009 and decreases
moving towards high solar activity year. This suggests that significant improvements to theIRI-2012 model (hmF2 model) are required particularly in the equatorial regions taking theimpacts of solar minimum year into account.

Keywords: Ionosphere; GPS; IRI model; Solar activity

Figure 1*Corresponding author: Sanjay Kumar, sanjay.skitvns@gmail.com
3Coupling of the High and Mid Latitude Ionosphere and Its Relation to Geospace Dynamics

FULL PAPER

Open AccessObservation of ionospheric disturbances induced by the2011 Tohoku tsunami using far-field GPS data in HawaiiLong Tang, Xiaohong Zhang* and Zhe Li
Earth, Planets and Space 2015, 67:88 DOI: 10.1186/s40623-015-0240-0
Received: 30 January 2015, Accepted: 22 April 2015, Published: 11 June 2015

Abstract
In this study, we employ far-field GPS total electron content (TEC) observed in Hawaii to detect the ionospheric disturbances
induced by the 2011 Tohoku tsunami. We observed tsunami-driven traveling ionospheric disturbances (TIDs) at two different
times: at about 12:40 UT, there were TIDs in the disturbance series propagating at approximately 260 m/s in an outward
direction from the tsunami’s source, and then, the signals began to weaken and gradually disappeared after 14:00 UT;
however, at about 17:30 UT, the TIDs appeared again in the disturbance series with similar propagation characteristics.
According to the observation times, the former TIDs can be attributed to the straight tsunami from the mainshock, while thelatter TIDs are most likely driven by tsunami from aftershocks. Furthermore, we
also observed tsunami-like TIDs at about 11:50 UT with similar horizontal velocity
and direction compared to tsunami waves. However, the arrival time of the TIDs
was about 1.5 earlier than tsunami waves in the sea level and should be inducedby other sources.

Keywords: GPS; Total electron content; Traveling ionospheric disturbances;
TsunamiFigure 1*Corresponding author: Xiaohong Zhang, xhzhang@sgg.whu.edu.cn

FULL PAPER

Open Access

Simultaneous ground-based optical and SuperDARN
observations of the shock aurora at MLT noon
Jianjun Liu*, Hongqiao Hu, Desheng Han, Huigen Yang and Mark Lester
Earth, Planets and Space 2015, 67:120 DOI: 10.1186/s40623-015-0291-2
Received: 21 December 2014, Accepted: 8 July 2015, Published: 29 July 2015

Abstract
Using ground-based high temporal and spatial optical aurora observations, we investigated one fortuitous event to illustrate the direct
responses of the fine structure auroral emission to interplanetary shock on 7 January 2005. During the shock impact to the magnetosphere,
the Chinese Arctic Yellow River Station (YRS) equipped with all-sky imagers (ASIs) was situated at the magnetic local noon region (~1210 MLT)in the Northern Hemisphere, while the SuperDARN CUTLASS Finland HF radar covering the fieldof view (FOV) of the ASIs at YRS had fine ionospheric plasma convection measurement. We
observed that an intensified red aurora manifesting as a discrete emission band at a higher
latitude responds to the shock impact gradually, which results in a distinct broadening of thedayside auroral oval due to the equatorward shifting of its lower latitude boundary after theshock arrival. In contrast, the green diffuse aurora, manifesting as a relatively uniform
luminosity structure, reacts immediately to the shock compression, displaying prompt
appearance in the southern edge of the FOV and subsequent poleward propagation of its
higher latitude boundary. Simultaneously, the CUTLASS Finland radar monitored enhanced
backscatter echo power and increased echo number, which coincided with intensified discrete
aurora in approximately the same latitudinal region. Doppler velocity measurement showedmoving ionospheric irregularities with generally enhanced line-of-sight (LOS) speed, but withprominent sunward flow in the polar cap and antisunward flow in both the eastern and westernregions. The SuperDARN global ionospheric convection pattern clearly presented a large-scale
plasma flow divided in four circulation cells, with two reversed flow cells nested in the noon
sector of the polar cap. These direct observations strongly suggest that the prompt shockcompression intensified the wave-particle interaction in the inner magnetosphere andenhanced the lobe magnetic reconnection rate at magnetospheric high latitude.

Keywords: Interplanetary shock; Sudden impulse; Optical aurora; SuperDARN;
Sunward flow

Figure 1*Corresponding author: Jianjun Liu, liujianjun@pric.org.cn
4Earth, Planets and Space

FULL PAPER

Open Access

Method for modeling of the components of ionospheric parametertime variations and detection of anomalies in the ionosphere
Oksana V. Mandrikova*, Nadejda V. Fetisova, Yuri A. Polozov, Igor S. Solovev and Mikhail S. Kupriyanov
Earth, Planets and Space 2015, 67:131 DOI: 10.1186/s40623-015-0301-4
Received: 31 December 2014, Accepted: 4 August 2015, Published: 18 August 2015

Abstract
In this study, a new multicomponent model (MCM) to determine the time variation of ionospheric parameters is suggested.
The model was based on the combination of wavelets with autoregressive-integrated moving average model classes andallowed the study of the seasonal and diurnal variations of ionospheric parameters and the determination of anomalies
occurring during ionospheric disturbances. To investigate in detail anomalous changes in the ionosphere, new computational
solutions to detect anomalies of different scales and estimate their parameters (e.g., time of occurrence, duration, scale, andintensity) were developed based on a continuous wavelet transform. The MCM construction
for different seasons and periods of solar activity was described using ionosphere criticalfrequency fo F2 data from Kamchatka (Paratunka Station, 52° 58′ N, 158° 15′ E, Institute of
Cosmophysical Research and Radio Wave Propagation FEB RAS). A comparison of the MCM
with the empiric International Reference Ionosphere (IRI) model and the moving medianmethod for the analyzed region showed that the suggested method was promising for
future research, since it had the advantage of providing quantitative estimates for theoccurrence time, duration, and intensity of the anomalies, characterizing the ionosphericstate and disturbance degree with a higher accuracy. Geomagnetic storms from 17 Marchand 2 October 2013 were analyzed using the suggested method, and it was shown that theionospheric disturbances were at maximum during the strongest geomagnetic
disturbances. An increase in the electron concentration in comparison with the backgroundlevel, under calm or weakly disturbed geomagnetic field conditions, was identified before
the analyzed magnetic storms.

Keywords: Wavelet transform; Autoregressive-integrated moving average model;
Ionosphere critical frequency; Ionospheric disturbances

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

FULL PAPER

Open Access

Application of ground scatter returns for calibration of HF
interferometry data
Pavlo Ponomarenko*, Nozomu Nishitani, Alexey V. Oinats, Taishi Tsuya and Jean-Pierre St.-Maurice
Earth, Planets and Space 2015, 67:138 DOI: 10.1186/s40623-015-0310-3
Received: 21 March 2015, Accepted: 19 August 2015, Published: 26 August 2015

Abstract
Information on the vertical angle of arrival (elevation) is crucial in determining propagation modes of high-frequency (HF,
3–30 MHz) radio waves travelling through the ionosphere. The most advanced network of ionospheric HF radars, SuperDARN(Super Dual Auroral Radar Network), relies on interferometry to measure elevation, but this information is rarely used due tointrinsic difficulties with phase calibration as well as with the physical interpretation of the measured elevation patterns. In
this work, we propose an empirical method of calibration for SuperDARN interferometry. The method utilises a well-defined
dependence of elevation on range of ground scatter returns. “Fine tuning” of the phase is achieved based on a detailed
analysis of phase fluctuation effects at very low elevation angles. The proposed technique has been successfully applied todata from the mid-latitude Hokkaido East SuperDARN radar. It can also be used at any other installation that utilises HF
interferometry.

Keywords: Ionospheric radio wave propagation; High-frequency radars; Interferometry

Figure 1*Corresponding author: Pavlo Ponomarenko, pasha.ponomarenko@usask.ca
5Coupling of the High and Mid Latitude Ionosphere and Its Relation to Geospace Dynamics

FULL PAPER

Open AccessThree-dimensional electron density along the WSA and
MSNA latitudes probed by FORMOSAT-3/COSMIC
F. Y. Chang, J. Y. Liu*, L. C. Chang, C. H. Lin and C. H. Chen
Earth, Planets and Space 2015, 67:156 DOI: 10.1186/s40623-015-0326-8
Received: 8 December 2014, Accepted: 7 September 2015, Published: 21 September 2015

Abstract
In this paper, we employ electron density profiles derived by the GPS radio occultation
experiment aboard the FORMOSAT-3/COSMIC (F3/C) satellites to examine the electron
density on geographic latitudes of 40° to 80° in the Southern hemisphere and 30° to 60° in
the Northern hemisphere at various global fixed local times from February 2009 to January
2010. The results reveal that an eastward shift of a single-peak plasma density feature occurs
along the Weddell Sea Anomaly (WSA) latitudes, while a double-peak plasma density featureappears along the northern Mid-latitude Summer Nighttime Anomaly (MSNA) latitudes. A
cross-comparison between three-dimensional F3/C electron density and HWM93 simulation
confirms that the magnetic meridional effect and vertical effect caused by neutral winds
exhibit the eastward shifts. Furthermore, we find that the eastward shift of the peaks whenviewed as a function of local time suggests that they could be interpreted as being
comprised of different tidal components with distinct zonal phase velocities in local time.

Keywords: FORMOSAT-3/COSMIC; WSA; MSNA; Neutral wind effectFigure 1*Corresponding author: J. Y. Liu, jyliu@jupiter.ss.ncu.edu.tw

FULL PAPER

Open Access

Daytime gigahertz scintillations near magnetic equator: relationshipto blanketing sporadic E and gradient-drift instability
Aramesh Seif*, Roland T. Tsunoda, Mardina Abdullah and Alina Marie Hasbi
Earth, Planets and Space 2015, 67:177 DOI: 10.1186/s40623-015-0348-2
Received: 3 March 2015, Accepted: 26 October 2015, Published: 4 November 2015

Abstract
Observations made in non-equatorial regions appear to support the hypothesis that the daytime scintillation of radio signals
at gigahertz (GHz) frequencies is produced by the gradient-drift instability (GDI) in the presence of a blanketing sporadic E(Esb) layer. However, the only evidence offered, thus far, to validate this notion, has been some observations of Esb in thevicinity of GHz scintillations. A more comprehensive evaluation requires information about electric field, together with thepresence of a steep gradient, which is presumed to be that of Esb. In this regard, the region in the vicinity of the equatorial
electrojet (EEJ) appears to be an ideal “laboratory” to conduct such experiments. The dominant driver of electron drift there is
the same as that of the EEJ, the vertical polarization electric field, and indications are that the presence of Esb in that vicinity iscontrolled by a balance in horizontal transport of Esb, between the EEJ electric field and the neutral wind, as described in amodel by Tsunoda (On blanketing sporadic E and polarization effects near
the equatorial electrojet, 2008). In this paper, we present, for the first time,
results from a comprehensive study of daytime GHz scintillations near themagnetic equator. The properties, derived from measurements, are shown,for the first time, to be consistent with a scenario in which Esb presence isdictated by the Tsunoda model, and the plasma-density irregularities
responsible for GHz scintillations appear to be produced by the GDI.

Keywords: Daytime GHz scintillation; Blanketing sporadic E (Esb); Magnetic
dip equator; Equatorial electrojet (EEJ)

Figure 1*Corresponding author: Aramesh Seif, arameshseif@gmail.com
6

Earth, Planets and SpaceLETTER

Open AccessOccurrence characteristics and lowest speed limit of subauroralpolarization stream (SAPS) observed by the SuperDARN
Hokkaido East radar
Hiroki Nagano, Nozomu Nishitani* and Tomoaki Hori
Earth, Planets and Space 2015, 67:126 DOI: 10.1186/s40623-015-0299-7
Received: 31 March 2015, Accepted: 3 August 2015, Published: 13 August 2015

Abstract
We investigate the characteristics of the subauroral polarization stream (SAPS), with focus on the relationship between
geomagnetic parameters and occurrence characteristics of SAPS. This study’s observations were made using the Super Dual
Auroral Radar Network (SuperDARN) Hokkaido East radar, which can observe the Far East region of Russia and has been in
operation since 2006. In particular, we identify the lowest limit of SAPS speed, which has not been discussed in previous
literature, in order to examine the lowest threshold of electric field able to generate SAPS as a result of magnetosphereionosphere (M-I) coupling. In order to conduct a comprehensive investigation of SAPS occurrence characteristics, we analyzed
events with wider ranges of velocity and magnetic latitude (MLAT) than those in previous studies. As a result of quantitative
estimation, we found two categories of westward flows that were reasonably
separated using a speed threshold of 150–200 m/s. For the faster flows above thespeed threshold, there is a clear correlation between MLAT and SYM-H geomagnetic
index, whereas for the slower flows, there is no such correlation. The faster flows are
considered to be SAPS, whereas the slower flows are probably associated with
mid-latitude F-region ionospheric irregularities not directly related to storms or
substorms. This slowest limit of SAPS gives us a minimum electric field of 7.5–10
mV/m that generates SAPS. However, this field strength is not strong enough tocause frictional heating, which is generally considered to be a crucial mechanism forgenerating SAPS. This result suggests that frictional heating is not always necessary
to generate SAPS.

Keywords: SAPS; Subauroral polarization stream; SuperDARN; Hokkaido East radar

Figure 1*Corresponding author: Nozomu Nishitani, nisitani@isee.nagoya-u.ac.jp

LETTER

Open Access

Strong induction effects during the substorm on 27 August
2001
V. V. Mishin*, V. M. Mishin, S. B. Lunyushkin, Z. Pu and C. Wang
Earth, Planets and Space 2015, 67:162 DOI: 10.1186/s40623-015-0333-9
Received: 19 February 2015, Accepted: 23 September 2015, Published: 5 October 2015

Abstract
We report on strong induction effects notably contributing to the cross polar cap potential drop and the energy balance
during the growth and active phases of the substorm on 27 August 2001. The inductance of the magnetosphere is found tobe crucial for the energy balance and electrical features of the magnetosphere in thecourse of the substorm. The inductive response to the switching on and off of thesolar wind-magnetosphere generator exceeds the effect of the interplanetary
magnetic field (IMF) variation. The induction effects are most apparent during thesubstorm expansion onset when the rapid growth of the ionospheric conductivity isaccompanied by the fast release of the magnetic energy stored in the magnetotail
during the growth phase. Using the magnetogram inversion technique, weestimated the magnetospheric inductance and effective ionospheric conductivity
during the loading and unloading phases.

Keywords: Substorm loading and unloading phases; Electromagnetic induction;
Polar cap magnetic flux

Figure 1*Corresponding author: V. V. Mishin, vladm@iszf.irk.ru
7

Coupling of the High and Mid Latitude Ionosphere and Its Relation to Geospace Dynamics

LETTER

Open Access

Statistical characteristics of medium-scale traveling ionospheric disturbances
revealed from the Hokkaido East and Ekaterinburg HF radar data
Alexey V. Oinats*, Nozomu Nishitani, Pavlo Ponomarenko, Oleg I. Berngardt
and Konstantin G. Ratovsky
Earth, Planets and Space 2016, 68:8 DOI: 10.1186/s40623-016-0390-8
Received: 31 March 2015, Accepted: 15 January 2016, Published: 21 January 2016

Abstract
We present a statistical study of medium-scale traveling ionospheric disturbances (MSTIDs) using the Hokkaido East (43.53° N,
143.61° E) and Ekaterinburg (56.42° N, 58.53° E) high-frequency (HF) radar data. Radar datasets are available from 2007 to 2014
for the Hokkaido and from 2013 to 2014 for the Ekaterinburg radar. In the case of the Hokkaido East radar, we have utilized theelevation angle information to study the MSTIDs propagating at the heights of the E and F ionospheric regions separately. We
have analyzed the diurnal and seasonal behavior of the following medium-scale traveling ionospheric disturbance (MSTID)
parameters: propagation direction, apparent horizontal velocity and wavelength, period, and relative amplitude. The F region
MSTID azimuthal patterns were observed to be quite similar by the two radars. The E region northwestward MSTIDs (from 280°
to 320°) were typical of summer daytime. Comparison with the horizontal windmodel (HWM07) has showed that the dominant MSTID propagation directions matchthe anti-wind direction well, at least during sunlight hours. We have also found thatthe wavelength and period tend to decrease with an increase in solar activity. On thecontrary, the relative amplitude increases with an increase in solar activity. Moreover,
the relative amplitude tends to increase with increasing auroral electrojet (AE) index,
as do the wavelength and velocity.

Keywords: Medium-scale traveling ionospheric disturbances; Atmospheric gravity
waves; High-frequency radar; Hokkaido East SuperDARN radar;
Ekaterinburg HF radar

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

LETTER

Open Access

Diurnal and seasonal behavior of the Hokkaido East
SuperDARN ground backscatter: simulation and observation
Alexey V. Oinats*, Nozomu Nishitani, Pavlo Ponomarenko and Konstantin G. Ratovsky
Earth, Planets and Space 2016, 68:18 DOI: 10.1186/s40623-015-0378-9
Received: 31 March 2015, Accepted: 31 December 2015, Published: 9 February 2016

Abstract
We studied regular diurnal and seasonal behaviors of ground backscatter propagation characteristics corresponding to the Hokkaido
East Super Dual Auroral Radar Network (SuperDARN) (43.53° N, 143.61° E). Firstly, we simulated key propagation characteristics using
a high frequency (HF) calculation technique based on the waveguide approach and International Reference Ionosphere (IRI)-2012
model as background ionosphere. The minimum slant range, skip distance, corresponding elevation angle, and true reflection height
were considered in this study. The behaviors of these characteristics were well explained by diurnal and seasonal variations in thecritical frequency and maximum height of corresponding ionosphere layer in HF reflection point. We estimated the accuracy of thestandard SuperDARN mapping technique and proposed a means for its improvement. Secondly, we constructed an algorithm formass data processing and extracted diurnal dependencies of the minimum slant range, corresponding elevation angle, and effective
reflection height from the Hokkaido East SuperDARN dataset for a period from 2007 to 2014. The algorithm uses the simulatedcharacteristics for distinguishing regular ground backscatter echoes propagating in the E and F2 HF channels. Observed monthly
mean and simulated values of the characteristics were compared, and the result showed that the accuracy of IRI-2012 significantly
depends on solar activity level and orientation of HF propagation path. In general, the difference between observed and simulated
values decreased with increases in solar activity and azimuth. We also
analyzed the occurrence of echoes originating behind the radar and foundathat they most frequently appear in winter and equinoxes before sunrise inbeam #0 and after sunset in beam #15. The probability of their observation
for a specific local time could reach up to 35 %.

Keywords: High-frequency wave ionospheric propagation;

International reference ionosphere; Hokkaido East
SuperDARN radar*Corresponding author: Alexey V. Oinats, oinats@iszf.irk.ru
8

Figure 1

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Contents
Special issue “Coupling of the high and mid latitude ionosphere and its relation to geospace dynamics”. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Nozomu Nishitani, Tsutomu Nagatsuma, Akira Sessai Yukimatu, Hongqiao Hu and Takeshi Sakanoi
IMF-By dependence of transient ionospheric flow perturbation associated with sudden impulses: SuperDARN
observations. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Tomoaki Hori, Atsuki Shinbori, Shigeru Fujita and Nozomu Nishitani
Impacts of solar activity on performance of the IRI-2012 model predictions from low to mid latitudes. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Sanjay Kumar, Eng Leong Tan and Dhimas Sentanu Murti
Observation of ionospheric disturbances induced by the 2011 Tohoku tsunami using far-field GPS data in Hawaiii. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Long Tang, Xiaohong Zhang and Zhe Li
Simultaneous ground-based optical and SuperDARN observations of the shock aurora at MLT noon
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Jianjun Liu, Hongqiao Hu, Desheng Han, Huigen Yang and Mark Lester
Method for modeling of the components of ionospheric parameter time variations and detection of anomalies in theionosphere . . . . . . . . . . . . . . . . . . Oksana V. Mandrikova, Nadejda V. Fetisova, Yuri A. Polozov, Igor S. Solovev and Mikhail S. Kupriyanov
Application of ground scatter returns for calibration of HF interferometry data
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Pavlo Ponomarenko, Nozomu Nishitani, Alexey V. Oinats, Taishi Tsuya and Jean-Pierre St.-Maurice
Three-dimensional electron density along the WSA and MSNA latitudes probed by FORMOSAT-3/COSMIC. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . F. Y. Chang, J. Y. Liu, L. C. Chang, C. H. Lin and C. H. Chen
Daytime gigahertz scintillations near magnetic equator: relationship to blanketing sporadic E and gradient-drift
instability. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Aramesh Seif, Roland T. Tsunoda, Mardina Abdullah and Alina Marie Hasbi
Occurrence characteristics and lowest speed limit of subauroral polarization stream (SAPS) observed by the SuperDARN
Hokkaido East radar. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Hiroki Nagano, Nozomu Nishitani and Tomoaki Hori
Strong induction effects during the substorm on 27 August 2001
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . V. V. Mishin, V. M. Mishin, S. B. Lunyushkin, Z. Pu and C. Wang
Statistical characteristics of medium-scale traveling ionospheric disturbances revealed from the Hokkaido East andEkaterinburg HF radar data
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Alexey V. Oinats, Nozomu Nishitani, Pavlo Ponomarenko, Oleg I. Berngardt and Konstantin G. Ratovsky
Diurnal and seasonal behavior of the Hokkaido East SuperDARN ground backscatter: simulation and observation. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Alexey V. Oinats, Nozomu Nishitani, Pavlo Ponomarenko and Konstantin G. Ratovsky

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Cover image: Nagano, H. et al., Earth, Planets and Space 2015, 67:126 DOI: 10.1186/s40623-015-0299-7