PEM27-01

Room:A01

Time:May 25 17:15-17:30

Development of wideband impedance probe system for observation of the ionosphric ioncomposition
KUMAMOTO, Atsushi1∗
1

Tohoku University

Concept and design of new wideband impedance probe system for observation of the ionospheric ion composition have been
investigated. Impedance probe system for measurement of the electron number density, which is called NEI, were developed
by Oya [1966], and successfully utilized for numerous sounding rockets and spacecraft such as Denpa, Taiyo, Jikiken, Hinotori,
Ohzora, and Akebono [e.g. Wakabayashi et al., 2013]. NEI measures the equivalent capacitance of the probe immersed in themagnetized plasma. By applying RF signal to the probe, we can identify the minimum of equivalent capacitance due to upperhybrid resonance (UHR). The frequency of RF signal is swept from 100 kHz to 25 MHz, in order to cover the UHR frequency
range in the Earth’s ionosphere. The equivalent capacitance of the probe in the magnetized plasma shows minimum not only
at UHR frequency but also at another resonance frequency: Lower hybrid resonance (LHR). If we can measure LHR frequency
with UHR frequency and electron cyclotron frequency, we can derive effective mass of ionospheric plasma and determine theionospheric ion compositions. Because LHR frequency is about several kHz in the ionosphere, we have to extend the lower
limit frequency of the current impedance probe system to 100 Hz. We changed the design of NEI as follows: (a) Coupling
capacitor between the circuits is changed in order to pass the low-frequency AC signals. (b) Because long time is needed for
frequency sweep in a low frequency range, high-frequency signal with short sweep period and low-frequency signal with longsweep period are combined and impressed to the probe in order to keep the high time resolution in the measurement of UHR
frequency. We have performed the chamber experiment with bread-board model (BBM) of wideband impedance probe system in
2014. We confirmed that the new impedance probe system could measure (1) UHR in high frequency range as well as the current
NEI could, and (2) equivalent capacitance profile from 100 Hz to 100 kHz, which indicates sheath capacitance of 120 pF andsheath resistance of 30 kohm. Unfortunately, LHR could not be identified in the chamber experiment because of high collision
frequency in the chamber. The detectability of LHR with the wideband impedance probe system have to be verified through the
future sounding rocket experiments in the ionosphere, where the collision frequency is enough low.
Keywords: Impedance probe, Ion composition, Sounding rocket, Chamber experiment, Lower hybrid resonance (LHR), Electron
number density

1/1

PEM27-02

Room:A01

Time:May 25 17:30-17:45

Study of the ionospheric plasma density structure observed by topside sounder on board
the EXOS-D (Akebono) satellite
HOSHI, Yasuto1∗ ; KATOH, Yuto1 ; KUMAMOTO, Atsushi11

Dept. Geophys., Grad. Sch. Sci., Tohoku Univ.

The electron number density, electron and ion temperature of the ionospheric trough in the polar ionosphere has been investigated based on the analysis of data obtained by Plasma Wave detectors and Sounder (PWS) system onboard the EXOS-D(Akebono) satellite.
Stimulated Plasma Wave experiments (SPW), one of the subsystems of PWS, enables us to conduct topside sounding of theionosphere and to measure the excitation of plasma resonances in the surrounding plasma [Oya et al., 1990]. In operation of
SPW in H-band normal sweep mode, RF pulse is transmitted with a swept frequency ranging from 0.3 MHz to 11.4 MHz within
32 sec. We measure the frequency and delay time of each echo found in the ionograms. We then divide the topside ionosphere
into multiple plasma layers, and determine group velocities in them, which are to be consistent with measured frequency anddelay. Finally, we can obtain the plasma density distribution of the topside ionosphere.
First, we analyze ionograms obtained by SPW in the region nearby European Incoherent Scatter (EISCAT) radar at (69.58 N,
19.23 E) (Tromso, Norway). We identified two events of ionospheric trough, in which the plasma density is depleted. One isfound at (65 N, 15 E) on Feb. 28, 1995 (hereafter called ”Event 1”), and the other is found at (70 N, 35 E) on Mar. 1, 1995
(hereafter called ”Event 2”). We also analyze simultaneous EISCAT UHF radar data with EXOS-D observations and find no
density depletion in the radar data.
Next, we derive the vertical profile of the scale height inside and outside the inospheric trough from the vertical profile of theelectron number density. The derived scale height at 500 km altitude inside the ionospheric trough of these 2 events is 20 % lessthan that outside the ionospheric trough. Assuming that the distribution of electrons and ions can be explained by the diffusive
equilibrium of the bipolar diffusion, we estimate the sum of electron and ion temperature from the scale height. The estimatedtemperatures are 3730 K inside the trough and 5070 K outside the trough found in Event 1, and 3290 K outside the trough and2940 K inside the trough in Event 2. These results indicate that the plasma temperature in the identified plasma depletion region
is lower than that in the surrounding region. Based on the explanation that the frictional heating increase the plasma temperature,and cause the plasma density depletion by the enhanced dissociative recombination, the plasma temperature in the trough have tobe higher than that outside the trough. The results do not agree with the expectation. However, in Event 1, the estimated plasma
temperature in the trough is higher than the plasma temperature (about 3000 K) obtained from IRI-2012 model at the observed
local time. So we can consider also that the plasma temperatures both inside and outside the trough was higher than normal
background ionospheric temperature. We also discuss the dependence of the temperature inside the trough on other control factor such as composition of ionospheric plasma, and unsteady control factor such as the geomagnetic activities.
Keywords: ionosphere, topside sounder, trough

1/1

PEM27-03

Room:A01

Time:May 25 17:45-18:00

A study of equatorial plasma bubbles by 630-nm airglow imaging observations from theInternational Space Station
YAMADA, Takanori1∗ ; OTSUKA, Yuichi1 ; SAKANOI, Takeshi2 ; YAMAZAKI, Atsushi3 ; KUBOTA, Minoru4 ;JIN, Hidekatsu4 ; SAITO, Akinori5 ; AKIYA, Yusuke5 ; HOZUMI, Yuta5
1

Solar-Terrestrial Environmental Laboratory, Nagoya University, 2 Planetary Plasma and Atmospheric Research Center, Graduate School of Science, Tohoku University, 3 Institute of Space and Astronautical Science / Japan Aerospace Exploration Agency,
4
National Institute of Information and Communications Technology, 5 Department of Geophysics, Graduate School of Science,
Kyoto University
In order to disclose global distribution of the upper atmosphere, Ionosphere, Mesosphere, upper Atmosphere, and Plasmasphere mapping mission (IMAP) on the International Space Station (ISS) started on October 2012. In this study, we analyzed
630-nm airglow images observed during a period from September 5, 2012 to August 28, 2013 by VISI (Visible and Infrared Spectral Imager), mounted on ISS to reveal the longitudinal characteristics of the equatorial ionosphere disturbances. We examined
the seasonal and longitudinal characteristics of the occurrence of the plasma bubbles, and found occurrence rate of the plasma
bubbles is high in spring and autumn equinoxes, especially at African longitudinal sector. This result is consistent with previous
studies. Furthermore, we measured zonal interval between the plasma bubbles and examined its longitudinal characteristics. We
found that plasma bubble intervals depend on longitude and that most of intervals are 100-200 km at 0-90o longitudinal sector
and 200-300 km at 225-360o longitudinal sector. In this study, we also compare the observed 630-nm airglow intensity with thatsimulated by GAIA(Ground-to-topside model of Atmosphere and Ionosphere for Aeronomy) model to discuss day-to-day andlongitudinal variations of equatorial ionization anomaly.
Keywords: plasma bubbles, ISS-IMAP

1/1

PEM27-04

Room:A01

Time:May 26 09:00-09:15

Comparison of neutral temperature with ion temperature in the polar lower thermosphere
TAKITA, Shintaro1∗ ; NOZAWA, Satonori1 ; OGAWA, Yasunobu2 ; KAWAHARA, Takuya3 ; TSUDA, Takuo4 ;SAITO, Norihito5 ; WADA, Satoshi5 ; TAKAHASHI, Toru1 ; FUJIWARA, Hitoshi6 ; HALL, Chris7 ;BREKKE, Asgeir8
1

Solar-Terrestrial Environment Laboratory, Nagoya University, 2 National Institute of Polar Research, 3 Faculty of Engineering, Shinshu University, 4 The University of Electro-Communications, 5 Advanced Photonics Technology Development Group,
RIKEN, 6 Faculty of Science and Technology, Seikei University, 7 Tromsoe Geophysical Observatory, The Arctic University ofTromsoe, 8 Faculty of Science, The Arctic University of Tromsoe
We will present results of comparison between the neutral temperature and the ion temperature at 100-110 km height above
Tromsoe (69.6o N, 19.2o E), Norway. We have conducted observations of the neutral temperature and the sodium density between
about 80 and 110 km with the sodium LIDAR at Tromsoe since October 2010. We have also obtained wind data by making
five directional observations since October 2012. To date, we have obtained temperature and sodium density data for about 2800
hours in total and about 1800 hours of wind data. For five winter observational seasons between 2010 and 2015, simultaneous
observations of the sodium LIDAR and the EISCAT UHF radar were conducted at altitudes between 100 and 110 km for 43
nights (about 250 hours).
Below 150 km in altitude at middle latitudes, due to collisions between the two species as well as absence of external heatsources, the ion temperature is thought to be almost the same as the neutral temperature. This is not the case in the polar lower
thermosphere because of the energy input from the magnetosphere. Major heat sources are Joule heating, auroral particle heating, and the electron-ion heat exchange. Among them, Joule heating is the strongest component in the lower thermosphere. To
evaluate contributions of these heat sources, as the first step, we have compared the neutral temperature obtained by the sodium
LIDAR with the ion temperature by the EISCAT UHF radar at altitudes between 100 and 110 km. In general, at and below about
105 km there seems to be a reasonable agreement between the temperatures, and the ion temperature tends to be higher than theneutral temperature with increasing height above 105 km. We will present the comparison results and also discuss the effect of
the Joule heating.

Keywords: sodium lidar, EISCAT radar, joule heating, atmosphere temperature, polar lower thermosphere

1/1

PEM27-05

Room:A01

Time:May 26 09:15-09:30

A case study on generation mechanisms of a sporadic sodium layer during a night of highauroral activity
TAKAHASHI, Toru1∗ ; NOZAWA, Satonori1 ; TSUDA, Takuo2 ; OGAWA, Yasunobu3 ; SAITO, Norihito4 ;HIDEMORI, Takehiro1 ; KAWAHARA, Takuya5 ; HALL, Chris6 ; FUJIWARA, Hitoshi7 ; BREKKE, Asgeir8 ;TSUTSUMI, Masaki3 ; WADA, Satoshi4 ; KAWABATA, Tetsuya1 ; OYAMA, Shin-ichiro1 ; FUJII, Ryoichi1
1

Solar-Terrestrial Environment Laboratory, Nagoya University, 2 The University of Electro-Communications, 3 National Instituteof Polar Research, 4 RIKEN Center for Advanced Photonics, RIKEN, 5 Faculty of Engineering, Shinshu University, 6 Tromso
Geophysical Observatory, The Arctic University of Tromso,, 7 Faculty of Science and Technology, Seikei University, 8 Faculty of
Science, The Arctic University of Tromso, Tromso, Norway
Generation mechanisms of sporadic sodium layers (SSLs) have been discussed for more than three decade. Proposed mechanisms are as follows: Es layer, chemical reaction enhancement due to a background temperature variation, gravity waves, meteor
deposition, and aurora particle spattering. However there are few studies that evaluate these mechanisms quantitatively based on
observational data. In this study, we have quantitatively evaluated generation mechanisms of a SSL based on observational dataobtained by multiple instruments at a high latitude station: Ramfjordmoen, Tromso, Norway (69.6o N, 19.2o E).
The sodium LIDAR observed an SSL at 2118 UT on 22 January 2012. The SSL was observed for 18 min with a maximum
sodium density of about 1.9x1010 m−3 at 93 km with a 1.1 km thickness. The EISCAT UHF radar observed a sporadic E layer(Es layer) above 90 km from 2000 to 2300 UT. After 2000 UT, the Es layer gradually descended and reached 94 km at 2118
UT when the SSL appeared at the same altitude. In this event, considering the abundance of sodium ions (10% or less), the Es
layer could provide only about 21% or less of the sodium atoms to the SSL. We have investigated a temporal development of
the normal sodium ion layer with consideration of chemical reactions and the effect of the (south-westward) electric field using
observational values of the neutral temperature, electron density, horizontal neutral wind, and electric field. This calculation
has shown that those processes, including contributions of the Es layer, would provide about 88% sodium atoms of the SSL.
Effects of meteor absorption and auroral particle spattering appear to be less important. Therefore, we have concluded that the
major source of the SSL was sodium ions in a normal sodium ion layer. Two processes-namely the downward transportation of
sodium ions from a normal sodium ion layer due to the electric field, and the additional supply of sodium ions from the Es layer
under relatively high electron density conditions (i.e., in the Es layer)-played a major role in generating the SSL in this event.
Furthermore, we have found that the SSL was located in a lower temperature region, and that the temperature inside the SSL did
not show any remarkable temperature enhancements.
Keywords: Sporadic sodium layer, sodium lidar, polar region, aurora, MLT

1/1

PEM27-06

Room:A01

Time:May 26 09:30-09:45

Derivation of the stratospheric temperature with the sodium lidar
HIBINO, Tatsuya1∗ ; NOZAWA, Satonori1 ; TSUDA, Takuo2 ; KAWAHARA, Takuya3 ; SAITO, Norihito4 ;WADA, Satoshi4 ; TAKAHASHI, Toru1 ; FUJIWARA, Hitoshi5 ; HALL, Chris6
1

Solar-Terrestrial Environment Laboratory, Nagoya University, 2 The University of Electro-Communications, 3 Faculty of Engineering, Shinshu University, 4 The RIKEN Center forAdvanced Photonics Technology Development Group, RIKEN, 5 Facultyof Science and Technology, Seikei University, 6 Tromso Geophysical Observatory, The Arctic University of Tromso, Tromso,
NorwayWe have derived the temperature in the upper stratosphere between 30 and 50 km by using Rayleigh scatter data obtained by
the sodium LIDAR at Tromsoe (69.6N, 19.2E), Norway. We have carried out observations of the neutral temperature and sodium
density between 80 and 110 km in the polar upper mesosphere and lower thermosphere for five winter seasons (October-March)
starting in October 2010 by using the sodium LIDAR. To date, about 2800 hours of data are obtained. Together with datasets
obtained by EISCAT radars, MF radar and meteor radar operated at the same observational field, we have studied the vertical
coupling of the atmosphere as well as the magnetosphere-ionosphere-thermosphere coupling. To facilitate these activities, amillimeter wave receiver for measuring minor constituent in the stratosphere/mesosphere/lower thermosphere will be installed at
the same observational field in the near future. In this talk, we will present results of the derivation of the neutral temperature in
the upper stratosphere (30-50 km) by using the sodium LIDAR.
A sodium LIDAR observations use the resonance scattering from sodium atoms in the sodium layer between 80 and 110 km.
We also successfully receive Rayleigh scattering light from the atmosphere between about 30 and 60 km. The upper height
depends on the background noise level, while the lower height limit is determined by contamination of Mie scatter light. We
calculated the temperatures between November 2011 and February 2012 with a 1 km resolution and compared them with thecalculated atmospheric temperatures with the ECMWF (The European Centre for Medium-Range Weather Forecasts) data. The
comparison shows a reasonable agreement.
This new addition of the datasets will make it possible to investigate the correlation of the temperature variation between theupper stratosphere (30-50 km) and the upper mesosphere/lower thermosphere (80-110 km). Furthermore, the observed stratospheric temperature will improve the accuracy of the millimeter wave observations.

Keywords: Sodium Lidar, Rayleigh scattering

1/1

PEM27-07

Room:A01

Time:May 26 09:45-10:00

Statistical study of probability of instabilities in the polar upper mesosphere/lower thermosphere
ASATO, Saki1∗ ; NOZAWA, Satonori1 ; FUJIWARA, Hitoshi2 ; KAWAHARA, Takuya3 ; TSUDA, Takuo4 ;TSUTUMI, Masaki5 ; SAITO, Norihito6 ; WADA, Satoshi6 ; KAWABATA, Tetsuya1 ; TAKAHASHI, Toru1 ;HALL, Chris7 ; BREKKE, Asgeir8
1

STEL, Nagoya University, 2 Faculty of Science and Technology, Seikei University, 3 Faculty of Engineering, Shinshu University,
The University of Electro-Communications, 5 National Institute of Polar Research, 6 Advanced Photonics Technology Development Group, RIKEN, 7 Tromsoe Geophysical Observatory, The Arctic University of Tromsoe, 8 Faculty of Science, The Arctic
University of Tromsoe
4

The aim of this study is to clarify probabilities of convective and dynamical instabilities and their variations in altitude/timein the polar upper mesosphere and lower thermosphere (80-110 km). In this study, we have used temperature data obtained withthe sodium LIDAR operated at the EISCAT Tromsoe (69.6N, 19.2E) site. Between October 2010 and January 2015, there are
287 nights when their temporal data lengths are equal to or longer than 4 hours on a night. Based on the temperature data, wehave calculated square of Brunt-Vaisala frequency (N2 ). The time and height resolution of the temperature data used are 10 min
and 1 km, respectively. Together with wind data obtained by the sodium LIDAR (after October 2012) or the co-located meteor
radar (before March 2012), we have also calculated Richardson numbers (Ri ) for the 287 nights. The instability probability on
one night is calculated as the percentage of the number of points whose N2 is negative for convective instability, and whose Ri
falls in the range of 0 <Ri <0.25 for dynamical instability to the total data set over the height region for the entire night.
Studies of probabilities of instabilities around the mesopause region were made at middle/low latitudes. Zhao et al. (JASTP,
65, 219-232, 2003) analyzed 32 nights (195 hours) of data sets over 1 year between June 1998 and May 1999 obtained at Starfire
Optical Range, near Albuquerque, NM (35N, 106.5W) and showed that the probabilities of static and dynamic instabilities were
maximum in mid-winter. Li et al. (JGR, 110, 2004JD005097, 2005) analyzed 19 nights of data sets obtained between January
2002 and November 2003 at Maui, Hawaii (20.7N, 156.3W), and pointed out that at any given time the probability that an unstable condition was found at some altitudes in the 85-100 km range was about 90%. To the best of our knowledge, no such a study
has been made for the polar upper mesosphere/lower thermosphere.
We will show probabilities of instabilities in the polar upper mesosphere and lower thermosphere, and difference of the probabilities in terms of year, month, and altitude. Furthermore, we will discuss correlations between the probabilities and amplitudesof tides/gravity waves and between the probabilities and auroral activity.

Keywords: polar upper mesosphere and lower thermosphere, convective instability, dynamical instability, sodium LIDAR, Tromsoe

1/1

PEM27-08

Room:A01

Time:May 26 10:00-10:15

Comparison of horizontal phase velocity distributions of gravity waves observed by ANGWIN,
using a 3D spectral technique
MATSUDA, Takashi S.1∗ ; NAKAMURA, Takuji2 ; EJIRI, Mitsumu K.2 ; TSUTSUMI, Masaki2 ;TAYLOR, Michael J.3 ; ZHAO, Yucheng3 ; PAUTET, P.-dominique3 ; MURPHY, Damian4 ;MOFFAT-GRIFFIN, Tracy5
1
4

SOKENDAI (The Graduate University for Advanced Studies), 2 National Institute of Polar Research, 3 Utah State University,
Australian Antarctic Division, 5 British Antarctic Survey

Atmospheric gravity waves (AGWs), which are generated in the lower atmosphere, transport significant amount of energy andmomentum into the mesosphere and lower thermosphere and cause the mean wind accelerations in the mesosphere. This momentum deposit drives the general circulation and affects the temperature structure. Among many parameters to characterize AGWs,
horizontal phase velocity is very important to discuss their vertical propagation. Airglow imaging is a useful technique for investigating the horizontal structures of AGWs around mesopause. An international airglow imager (and other instruments) networkin the Antarctic, named ANGWIN (Antarctic Gravity Wave Imaging/Instrument Network) was started in 2011. Its purpose is tounderstand characteristics of mesospheric gravity waves and their impacts on the Mesosphere and Lower Thermosphere (MLT)
environment over Antarctica.
In this study, we compared distributions of horizontal phase velocities of gravity waves at around 90 km altitude over different
locations using our new statistical analysis method based on 3-D Fourier transform, developed by Matsuda et al. (2014). The
comparison has been carried out for airglow imagers at four stations, that are, Syowa (69S, 40E), Halley (76S, 27W), Davis (69S,
78E) and McMurdo (78S, 156E), out of the ANGWIN imagers, for the observation period between April 6 and May 21 in 2013.
Not only horizontal propagation characteristics, gravity wave energies can also be quantitatively compared, indicating a smaller
GW activity in higher latitudes. The presentation will be focused on showing the performance of the new statistical technique
for studying gravity waves.

Keywords: atmospheric gravity wave, airglow imaging

1/1

PEM27-09

Room:A01

Time:May 26 10:15-10:30

A revisit to critical level blocking diagram
TOMIKAWA, Yoshihiro1∗
1

National Institute of Polar Research, 2 SOKENDAI

Matsuda et al. (2014) have proposed a new method to obtain a power spectral distribution of gravity waves in a horizontal
phase velocity domain from airglow observations. The obtained power spectral distribution can be interpreted as a product ofgravity wave source spectrum and wave transmissivity distributions under an assumption without wave dissipation/reflection andwave horizontal propagation. The gravity wave transmissivity depends on the existence of a critical level for the wave, which
is determined by background horizontal wind distributions. Taylor et al. (1993) have proposed a critical level blocking diagram
which represents a gravity wave transmissivity in a horizontal phase velocity domain. In this talk, the critical level blocking
diagram proposed by Taylor et al. (1993) will be revisited, and its amendment will be discussed. In addition, examples of thecritical level blocking diagram in some given background horizontal wind distributions will be shown.
Keywords: critical level, gravity wave, mountain wave

1/1

PEM27-10

Room:A01

Time:May 26 10:30-10:45

Gravity Waves in the Martian Atmosphere detected by the Radio Science Experiment
MaRS on Mars Express
TELLMANN, Silvia1∗ ; PATZOLD, Martin1
1

University of Cologne, Germany

Gravity waves are a ubiquitous feature in all stably stratified planetary atmospheres. They are known to play a significant role in
the energy and momentum budget of the Earth and they are assumed to be of importance for the redistribution of energy. This highvertical resolution of the radio occultation profiles from the MaRS experiment on Mars Express provides the unique opportunity
to study small scale vertical wave structures in the Martian lower atmosphere. These small scale temperature perturbations aremost probably caused by gravity waves (buoyancy waves) produced by the displacement of air masses flowing over elevatedtopographical features or other atmospheric sources like convection in the surface boundary layer or wind shear. A study ofthe global distribution of gravity waves provides insight into possible source mechanisms, local time dependencies, seasonal
dependencies and/or topographical dependencies.
Keywords: Mars, Mars Express, Gravity Waves, Atmosphere, Radio Occultation Experiment, Radio Science

1/1

PEM27-11

Room:A01

Time:May 26 11:00-11:15

Imaging of polar cap patches with small airglow cameras
HOSOKAWA, Keisuke1∗ ; OGAWA, Yasunobu2 ; TAGUCHI, Satoshi3
1

University of Electro-Communications, 2 National Institute of Polar Research, 3 Graduate School of Science, Kyoto University

In the last two decades, 630.0 nm airglow measurements with cooled CCD cameras have been widely used to observe various
kinds of ionospheric phenomena such as plasma bubble and MSTID. Recently, similar airglow observations at high-latitudes
have enabled us to visualize the dynamical behavior of polar cap patches, which are regions of high density plasma propagatingin the central polar cap region. In this sense, now the all-sky airglow measurement is one of the essential tools for monitoring
ionospheric phenomena at all the latitude regions. However, it is still very difficult to make a dense network of airglow imagers
and capture the large-scale structure in the ionosphere because the system is relatively large and high cost.
In this paper, we have employed a cheap and small CCD camera (Watec Co.Ltd.: WAT-910HX) to observe airglow in thepolar cap region and check if such a camera can be used for observations of polar cap patches. We prepared two sets of small
airglow camera, one with a fish-eye lens and the other with a wide field-of-view lens. They are combined with an optical filter
whose central wavelength is 632.0 nm, FWHM is 10 nm and transmittance is 85%. The two airglow cameras were installedin Longyearbyen (78.1N, 15.5E), Norway in October 2013 and operated continuously during the 2013/2014 winter season. In
Longyearbyen, airglow measurements with an EMCCD all-sky airglow imager (ASI) and the auroral spectrograph (ASG) havebeen carried out; thus, we were able to compare the images from the small airglow cameras with those from the conventional
airglow observation systems.
On the night of December 4, 2013, a series of polar cap patches was observed by the EMCCD all-sky imager in Longyearbyen.
The optical intensity of the patches was as large as 500 R. At the same time, the small airglow cameras also detected regions ofenhanced airglow intensity passing through their fields-of-view. The quality of the images was slightly lower than those from the
EMCCD-ASI, but it was high enough for capturing the 2D structure of the patches. This indicates that the small CCD cameraof Watec Co.Ltd. can be used for observations of ionospheric phenomena such as polar cap patches. However, there is some
sort of difference in the optical intensity between the EMCCD-ASI and the small airglow camera. We suppose that this is due tothe difference in the FWHM of the optical filters. In the presentation, we will discuss this difference in a quantitative manner byusing airglow spectra from ASG.
Keywords: Polar cap region, Polar cap patches, Airglow measurements

1/1

PEM27-12

Room:A01

Time:May 26 11:15-11:30

Measurements of neutral wind and plasma drift with chemical release in the cusp region- preliminary results
KAKINAMI, Yoshihiro1∗ ; KIHARA, Daiki1 ; WATANABE, Shigeto2 ; YAMAMOTO, Masa-yuki1 ; CONDE, Mark3 ;LARSEN, Miguel4
1

Kochi University of Technology, 2 Hokkaido Information University, 3 University of Alaska, Fairbanks, 4 Clemson University

A chemical release experiment was taken place on 24 November 2014 to measure neutral wind and plasma drift in the cusp
region, which was named the Cusp Region Experiment (C-REX). We set up 2 cameras (one for neutral Barium (Ba) and theother for ionized Barium (Ba+)) at Longyerben and Ny-Alsund for each site. In addition, one video camera at Ny-Alsund andone camera with a grating at Longyerben were set up. The rocket was launched from Andoya at 08:05 UT and first chemical
release was observed at 08:14:19 UT from Longyerben, Ny-Alsund and an airplane. Ten of 24 canisters were successfully ignited
between 200 and 400 km altitude at about 600 km away from Svalbard islands. Each canister contains barium (Ba) and strontium(Sr). Evaporated gasses reflect sunshine and green and blue “space fireworks” were observed by digital cameras with filter andvideo as well as human eyes. The filters were developed to observe resonance scattering of neutral Ba (552.5 nm) and ionized Ba(454.5 nm), and evaluated with an integrating sphere in National Institute of Polar Research. We also observed space fireworks
with a grating and successfully obtained spectrums. In this paper, we introduce our observation and show preliminary results ofthe experiment.
Keywords: cusp, neutral wind, plasma drift, space firework, chemical release exeprimet, neutral density anomaly

1/1

PEM27-13

Room:A01

Time:May 26 11:30-11:45

Detecting mid-latitude Es by InSARSUZUKI, Takato1∗ ; MAEDA, Jun1
1

Department of Natural History Sciences, Hokkaido University

Maeda and Heki. (2014) succeeded in capturing sporadic-E (Es) over Japan two-dimensionally, using the observation of
Global Positioning System ‒ Total Electron Content (GPS-TEC). While the GPS is originally used for the crustal deformation
monitoring, Interferometric Synthetic Aperture Radar (InSAR) is another space geodetic technique that allows us to detect crustal
movements. SAR transmits a microwave pulse and receives the reflected pulse while a target on the ground is in the beam byusing an antenna on the platform like aircrafts and satellites, so that it can implement virtually a large aperture antenna andcan create high-resolution images. InSAR can detect crustal deformation signals between the two acquisition dates as a twodimensional image by taking the difference of the phase data of the SAR images. Like GPS carrier phases, ionospheric effectsometimes appears on the InSAR images. The lower the used microwave frequency, the more notably the ionospheric effectappears. Hence, a satellite using L-band microwave like Advanced Land Observing Satellite (ALOS) is advantageous to detect
ionospheric phenomena. If Es can be detected by InSAR whose spatial resolution is higher than GPS, we can understand its
spatial structure in more detail and help to clarify the generation mechanism of the Es. In this study, we aimed to detect Es overJapan by InSAR.
First, we chose the dates whose critical frequencies of Es (foEs) were more than 15MHz at ionosonde in Wakkanai, Kokubunji
and Yamagawa in the morning in 2006 through 2010 from May to August. Second, we chose the data of ALOS/PALSAR whose
observing areas and dates are as close as possible, and generated interferometric images. An interesting phase shift appeared on
one of the images, the pair of March 28, 2009 (Master) and Jun 28, 2009 (Slave), and it had northeast direction slope. Although
the entire shape could not be imaged due to the sea surface, we could observe four patches; the spatial scale of each patch isabout 20km. Converting this phase shift into TEC variation (4TEC), it turns out that 4TEC=0.44TECU, which is close to whenEs appears. However, we could not identify the altitude in the InSAR image, and thus we used GPS-TEC. As a result, a similar
signal was detected near the place where the phase shift appeared on the InSAR image. We could identify the altitude of thesignals to be 100km. Therefore, it turns out that the phase shift on the InSAR image is caused by mid-latitude Es.

Keywords: InSAR, sporadic-E, GPS-TEC

1/1

PEM27-14

Room:A01

Time:May 26 11:45-12:00

Tidal effect of the neutral atmosphere in the lower thermosphere on the movement ofsporadic E at midlatitude
MAEDA, Jun1∗ ; HEKI, Kosuke1
1

Hokkaido University

Introduction
Sporadic E is a highly ionized plasma patch unpredictably appears at an altitude of ˜100 km in the E -region of the ionosphere.
At midlatitudes, occurrences maximize in local summer (Whitehead, 1989 and references there in), and in the Far East region
including Japan (Wu et al., 2005; Arras et al., 2008). Ground-based radar observations and rocket experiments have been thetwo primary methods of sporadic E observations. Since their spatial and temporal resolutions are restricted, two-dimensional(2-D) and/or continuous observations of sporadic E plasma patches and their movements have been difficult. Maeda and Heki[2014] have performed 2-D observations of midlatitude sporadic E by using dual-frequency Global Navigation Satellite System(GNSS) satellites and a dense array of GNSS receivers in Japan (GEONET) composed of ˜1200 GNSS staions. Sporadic E canbe observed as positive total electron content (TEC) anomaly in the GNSS-TEC observations. Mapping these anomalies revealed
2-D horizontal structure of sporadic E plasma patches and time sequences of TEC maps showed temporal evolution of the plasma
structure, including their movements.
AnalysesIn the present study, we use GNSS-TEC observations with GEONET receivers. We focus on the movement of sporadic E
patches. Typically sporadic E plasma patches form frontal structure that elongates 50-500 km in the east-west (E-W) direction[Maeda and Heki, 2014]. Since the movements in the E-W direction cannot be distinguished from the development of elongation,
here we only study movements in the N-S directions. 5 min TEC maps are generated to study temporal evolution of plasma
patches. Direction and speed of movements are manually read by 20-30 min interval. In total, 27 cases of sporadic E movements
over Kanto region are analyzed.
Results and Discussion
We counted the number of northward and southward movements, respectively, and plotted in the local time (LT) order. The
histogram shows LT dependence of N-S movements, i.e., northward and southward movements concentrates in the 10-12 LT and
18 LT, respectively. In between the two peaks, there is a silent period, i.e., the minimum of the number of movements at 15 LT.
These results are consistent with those reported by Tanaka [1979] who conducted backscatter radar observations in Kanto region(the same study area as ours). Tanaka [1979] showed that the westward movement peaks around 15 LT. Since we ignored theE-W movements, the silent period in the N-S movements can be interpreted as the results of rotation of movement directions ofplasma patches possibly governed by atmospheric tide. Thus, GNSS-TEC observations of sporadic E plasma patches may be
useful to infer the dynamics of the neutral atmosphere in the lower thermosphere.

Keywords: sporadic-E, GPS, TEC, atmospheric tide

1/1

PEM27-15

Room:A01

Time:May 26 12:00-12:15

Imaging observation of spatial structure of sporadic E layer by Magnesium Ion Imager on
the sounding rocket S-520-29
KURIHARA, Junichi1∗ ; IWAGAMI, Naomoto2 ; KOIZUMI-KURIHARA, Yoshiko3 ; TANAKA, Makoto4 ;TAKAHASHI, Takao4 ; ABE, Takumi3
1

Faculty of Science, Hokkaido University, 2 Graduate School of Science, The University of Tokyo, 3 Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency, 4 ICT Education Center, Tokai University
To study the spatial structure of midlatitude sporadic E (Es) layers, the vacuum ultraviolet resonant scattering by magnesium
ions (Mg+ ) in an Es layer was observed with the Magnesium Ion Imager (MII) on the sounding rocket S-520-29. Since the Es
layers is formed by the convergence of metallic ions that have slow ion-electron recombination rates, the distribution of Mg+ ,which is one of the dominant species among the metallic ions, is thought to reflect the spatial structure of the Es layer. It issuggested that the spatial structure of the Es layer is closely related to various ionospheric phenomena such as the field aligned
irregularity and the E-F coupling. Therefore, it is expected that imaging observations of the Mg+ distribution will provide newknowledge in the spatial structure of the Es layer.
The sounding rocket S-310-38 was launched from the Uchinoura Space Center in Kagoshima, Japan, on 6 February 2008 forthe same purpose and the two-dimensional horizontal structure of Mg+ in an Es layer was observed for the first time. While
this result demonstrates the usefulness of Mg+ imaging for understanding the spatial structure of Es layers, the attitude of thesounding rocket, especially the zenith angle of the rocket axis was unusually tilted and the area of meaningful observation was
limited.
In the sounding rocket S-520-29 experiment conducted on 17 August 2014, the MII was improved since the S-310-38 experiment and an attitude control system by gas jet was implemented. Unfortunately, the attitude control did not work as expected, but
the Mg+ distribution was successfully observed and important information on the spatial structure of the Es layer was obtained.

1/1

PEM27-16

Room:A01

Time:May 26 12:15-12:30

Ampere force exerted by geomagnetic Sq currents and thermospheric pressure difference
TAKEDA, Masahiko1∗
1

Data Analysis Center for Geomagnetism and Space Magnetism., Kyoto Univ.

Relationship between Ampere force exerted by geomagnetic Sq currents and neutral pressure was examined. It was shownthat the Ampere force around the Sq current vortex center is almost equal to the pressure difference between its maximum andminimum, and this balance is kept through the solar cycle. The lowest height of the pressure integration for best fit is 120km,
which is reasonable considering the height profile. There was a seasonal variation that the pressure difference is smaller andlarger in local summer and winter, respectively. This is consistent with the effects of magnetic field by inter-hemispheric fieldaligned currents on geomagnetic Sq field.

Keywords: geomagnetic daily variation, total current, Ampere force, thermospheric pressure difference, solar acivity

1/1

PEM27-17

Room:A01

Time:May 26 12:30-12:45

Study of ionospheric disturbances using the remote HF wave receiver of the SuperDARN
Hokkaido East radar
NISHITANI, Nozomu1∗ ; KIGAWA, Ryusuke1 ; HORI, Tomoaki1 ; HAMAGUCHI, Yoshiyuki1
1

Solar-Terrestrial Environment Laboratory, Nagoya University

We have been operating the remote HF wave receiver of the SuperDARN Hokkaido East radar in Nagoya and Rikubetsu (inthe vicinity of the HF radar) since 2014 to monitor the ionospheric disturbances. Using the remote receiver data it is possible
to monitor the upward / downward motion of the ionosphere at the ionospheric reflection point of the HF radar backlobe beams
emitted torward Nagoya areas. Initital result of the observation of ionospheric perturbations using the remote HF wave receiverof the SuperDARN Hokkaido East radar will be presented.
Keywords: SuperDARN, remote HF wave receiver, ionospheric disturbance

1/1

PEM27-18

Room:A01

Time:May 26 14:15-14:30

Seismo-traveling ionospheric disturbance observed by HF Doppler sounding system
CHOU, Min-yang1∗ ; TSAI, Ho-fang1 ; LIU, Jann-yenq2 ; LIN, Charles1
1

National Cheng-Kung University, 2 2Institute of Space Science, National Central University,

In this paper, networks and concurrent/co-located measurements of seismometers (BATS, K-net, KiK-net), HF Doppler Sounding Systems in Taiwan and Japan are used to study Seismo-traveling ionospheric disturbance (STIDs). It’s shown that theseinfrasound wave packets triggered by seismic surface waves that was generated by strong earthquake. The infrasound wave
packets were detected in the ionosphere at heights ˜200 km about 9 min after the detection of corresponding wave packets on the
ground. The individual wave packets recorded on the HF Doppler have different observed horizontal velocities and correspondto different type of seismic waves.
The Hilbert-Huang Transform (HHT) is applied to analyze Doppler frequency shifts (DFSs) detecting STIDs and estimatedthe amplification factor in vertical displacement of the ionosphere relative to the ground surface motion, while the time delay,
circle, ray-tracing, and beam-forming methods are used to compute the origin of the detected STIDs.

Keywords: STIDs, Ionosphere

1/1

PEM27-19

Room:A01

Time:May 26 14:30-14:45

Propagation Characteristics of Neutral Atmospheric Waves Associated with Earthquakes
Using a Numerical Simulation
YOSHIKAWA, Kouhei1∗ ; SHIMIZU, Yuki1 ; NAKATA, Hiroyuki1 ; TAKANO, Toshiaki1 ; MATSUMURA, Mitsuru2
1

Graduate School of Engineering, Chiba University, 2 National Institute of Polar Research

By using HF Doppler and GPS ionospheric total electron content (TEC) observations, it is found that atmospheric waves
excited by earthquakes cause ionospheric disturbances. In this study, we examined the relationship between seismic ground
perturbations and ionospheric disturbances in order to mechanism of the propagations of atmospheric waves using a numericalsimulation. In this simulation, we calculated temporal evolutions of neutral atmospheric waves by solving basic equations ofneutral atmosphere.
The effects of the artificial viscosity used in the numerical simulation are evaluated. In compressible fluids, shock waves
occur when advection velocity is faster than the sound velocity. Although shock waves correspond to discontinuous planes
mathematically, they have the thickness of the mean free path of air molecules approximately. When we run the simulation
without artificial viscosity, the simulation is diverged. Thus, we add Von-Neumann-type artificial viscosity. In adding theartificial viscosity, it is necessary to determine an adequate artificial viscosity coefficient. Therefore we compared the simulation
results with the theoretical equations (Chum et al ., 2012) obtained by subtracting attenuation from law of the conservation ofenergy flux. The simulation results were determined with the various artificial viscosities. As the artificial viscosity becomeslarger, the amplitude of simulation results become small and the amplitude depend on the period of input disturbance as comparedto the theoretical equations. This result means that the adequate artificial viscosity coefficient must be determined owing to theperiod of input disturbances. At the wave front, the waveform is elongated, the amplitude is larger than theoretical equation. We
discussed temporal waveforms to find the cause of this waveform. It is found that the waveform includes the lower frequency
component than input disturbance. The theoretical equation shows that the atmosphere works as low pass filter, and that the
cut-off frequency become lower with the higher altitude because high frequency components are attenuated due to viscosity andheat conduction. Due to these characteristics, low-frequency component is dominant at higher altitude.

Keywords: Earthquake, Neutral atmospheric wave, Numerical simulation, Ionospheric disturbance

1/1

PEM27-20

Room:A01

Time:May 26 14:45-15:00

Ca+ density perturbations observed by a resonance scattering lidar during MSTIDs
EJIRI, Mitsumu K.1∗ ; TSUDA, Takuo2 ; NISHIYAMA, Takanori1 ; ABO, Makoto3 ; NISHIOKA, Michi4 ;MARUYAMA, Takashi4 ; SAITO, Akinori5 ; NAKAMURA, Takuji1
1

National Institute of Polar Research, 2 The University of Electro-Communications, 3 Graduate School of System Design, Tokyo
Metropolitan University, 4 National Institute of Information and Communications Technology, 5 Department of Geophysics, Graduate School of Science, Kyoto University
In the mesosphere and lower thermosphere region, there are permanent layers of metal atoms and ions, the source of which
is vaporization of cosmic dust and meteoroids during their entry into the Earth’s atmosphere. Some metal atom layers e.g. Na,
K, Ca, and Fe layers, and only Ca+ (Calcium ion) can be observed by ground-based resonance scattering lidars. The National
Institute of Polar Research (NIPR) is developing a new resonance scattering lidar system with a frequency-tunable laser. The
lidar transmitter is based on injection-seeded, pulsed alexandrite laser for 768-788 nm and a second-harmonic generation (SHG)
unit for 384-394 nm. The new lidar is able to measure density variations of minor constituents including Ca+ (393 nm). As a partof the development, observation tests are carried out at NIPR (35.7N, 139.4E) since 2013, and we got the first light from Ca+ on
21 August, 2014. The Ca+ density profiles were obtained for ∼5 hours (23:13 LT-28:28 LT) with time and height resolutions of
1 min and 15 m, respectively. At the same night, sporadic E (Es ) layer was observed with an ionosonde at Kokubunji by National
Institute of Information and Communications Technology (NICT) (35.7N, 139.5E), also medium scale traveling ionospheric disturbances (MSTIDs) were observed with the dense GPS receiver network (GEONET). In this presentation, we compare thesedata in detail and discuss relationships between observed Ca+ density perturbations, Es layer and MSTIDs.
Keywords: resonance scattering lidar, Ca+, medium scale traveling ionospheric disturbances, GPS-TEC, sporadic E layer

1/1

PEM27-21

Room:A01

Time:May 26 15:00-15:15

Characteristics of spatial gradient of ionospheric TEC assoicated with plasma bubbles andits impact on GNSSSAITO, Susumu1∗ ; YOSHIHARA, Takayuki1
1Electronic Navigation Research Institute

The plasma bubble is a sharp depletion in the ionospheric plasma density. Spatial gradient of the ionospheric TEC (total electron content) associated with the sharp depletion of the plasma density makes it difficult for GNSS augmentation systems to work
properly. To mitigate the ionospheric threats associated with the spatial TEC gradient, it is important to know the characteristicsof the TEC gradient.
Data used are obtained in Ishigaki (24.3N, 124.2E) with five GNSS receivers with mutual distances from 86 to 1557 m. TEC
differences and thus the gradients between a pair of GNSS receivers are precisely derived with the single-frequency carrier-basedand code-aided (SF-CBCA) technique. Directions of the TEC gradients are estimated with the TEC gradients between threeof the five stations. The derived TEC gradients are compared with those derived with the dual-frequency TEC estimation withthe assumption that the TEC gradient in quiet time would be zero. The velocity and propagation directions of the gradients are
estimated with the correlation analysis of TEC variation of three of the five stations.
Associated with the plasma bubble events on 3 April 2008, the TEC gradients derived with the SF-CBCA method wasamounted to be 3.2 TECU/km, which is equivalent to the gradients in the ionospheric delay at L1 frequency of 518 mm/km.
It exceeds the upper bound of the ionospheric threat space (maximum assumed values in the safety design) of ground-based
augmentation system (GBAS). The result is proved to be realistic with the dual frequency measurements, though there seems tobe cycle-slip effects in TEC estimation. The velocity was estimated to be 118 m/s, and the propagation direction was estimatedto be 75 degrees. The propagation direction is consistent with the direction of the TEC gradient of 74 degrees (clockwise fromthe North). The spatial scale of the TEC gradient is estimated to be 7 km.
These parameters derived in this study are all relevant to the ionospheric threat space of GBAS, and the threat space is shown
to be modified so that this extreme TEC gradient is bounded. Thus, studying the characteristics of the TEC gradient with theparameters shown above are very important to the safety design of GNSS augmentation systems, and have to be investigatedextensively. Further analysis of the data obtained in the periods of higher solar activity than that of the event analyzed here isnecessary and is now going on.

Keywords: plasma bubble, ionospheric irregularity, TEC gradient, irregularity velocity, irregularity scale size, GNSS augmentation system

1/1