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

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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

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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

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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

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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

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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

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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

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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

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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

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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

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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

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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

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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

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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

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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.

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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

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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

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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

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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

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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

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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

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PEM27-P01

Room:Convention Hall

Time:May 26 18:15-19:30

Water vapor estimation using digital terrestrial broadcasting wave
KAWAMURA, Seiji1∗ ; OHTA, Hiroki1 ; HANADO, Hiroshi1 ; YAMAMOTO, Masayuki1 ; SHIGA, Nobuyasu1 ;KIDO, Kouta1 ; YASUDA, Satoshi1 ; GOTOH, Tadahiro1 ; ICHIKAWA, Ryuuichi1 ; AMAGAI, Jun1 ;IMAMURA, Kuniyasu1 ; FUJIEDA, Miho1 ; ISHIZU, Kentaro1 ; IWAI, Hironori1 ; SUGITANI, Shigeo1
1National Institute of Information and Communications Technology

We, National Institute of Information and Communications Technology (NICT), are developing a water vapor measurement
system using digital terrestrial broadcasting wave. Radio waves are delayed due to water vapor through propagation. Water
vapor can be retrieved by measuring this time delay. If the humidity increases by 1 %, radio waves delay by about 17 ps during
propagating 5 km distance. Very precise measurements (at least several tens of pico-second order) are needed for the effective
observations. Radio waves used for digital terrestrial broadcasting are modulated with OFDM, and known signals (SP signals) areembedded. Complex delay profiles are calculated using these known signals. Using the phase of delay profile, we can measurepropagation delay with precise accuracy (pico-second order). When we consider the accuracy with order of sub-nano seconds,
phase fluctuations of local oscillators at radio tower and receivers are essential error factors. So we measure the propagation delay
at two receiving points on the same line including the radio tower. Each result includes phase fluctuations of local oscillators atradio tower and receivers. Phase fluctuation of local oscillator at radio tower will be canceled out by taking the difference. We
can estimate water vapor between two receiving points by synchronization between their local oscillators.
We are developing a real-time delay (phase of delay profiles) measurement system with software-defined radio technique. We
have improved this system and maximum number of channels which can be processed in real-time has expanded to 5. Measurement accuracy of this system is evaluated, and the time resolution of measured delay time is found to about 50 ps. We plan to use
CATV to synchronize the local oscillators at different sites. Signals pass-through in the CATV network are the same RF signals
as that transmitted from the radio tower, and they can be also processed with the system mentioned above. Phase fluctuations oflocal oscillators at both sites are canceled out using the signals pass-through in CATV as references. Each signal pass-throughin CATV has its own delay due to the difference of network path. We have developed the method to correct it. The precision ofsynchronization is less than 100 ps, and in-house test is going on to improve it. We are planning demonstration experiments toestimate water vapor using two receiving stations in next summer. We will use optical fiber synchronization method, which isalready established by NICT, to evaluate CATV synchronization. We investigate miniaturization of measurement system using
DSP board for the multi-point measurement in the future.
Keywords: water vapor, radio wave, propagation delay, digital terrestrial broadcasting

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PEM27-P02

Room:Convention Hall

Time:May 26 18:15-19:30

Dual frequency observation of subionospheric perturbations associated with Hokuriku
winter lightning
MORINAGA, Yosuke1∗ ; TSUCHIYA, Fuminori1 ; OBARA, Takahiro1 ; MISAWA, Hiroaki1 ; HONMA, Yasunori2
1

Planetary Plasma and Atmospheric Research Center, Graduate School of Science, Tohoku University, 2 Tohoku Electric Power
Company
Intense electromagnetic pulses (EMP) radiated from lightning discharge could cause heating and ionization and alter the
conductivity in the ionospheric D-region. The purpose of this study is to reveal influence of the lightning on the lower ionosphereand its dependence on properties of lighting discharges. For this purpose, two LF radio observation systems were installed in
Takine (Fukushima) and Sasaguri (Fukuoka). Radio signals from two JJY transmitters at Haganeyama (Fukuoka, 60kHz) andOtakadoyayama (Fukushima, 40kHz) are simultaneously measured at Takine and Sasaguri, respectively. Radio propagation pathsof both transmitter ? receiver pairs are almost overlapped and the midpoints of both paths are located over the coast of Hokuriku
area. These enable us to investigate the lightning effect on the lower ionosphere at different height because it is expected thatreflection height of radio wave depends on radio frequency.
The LF signature of subionospheric perturbations associated with winter lightning in the Sea of Japan (around Hokuriku) has
been observed from December 13, 2014. Signatures of subionospheric perturbation (early event) which occur immediately after
the causative lightning were detected. While modeling studies (E. D. Schmitter. 2014) show that change of ionization state in
the lower ionosphere depends on intensity of EMP, there is no clear observation evidence that shows quantitative relationshipbetween them. We analyze the data derived from these observations using peak current of causative lightning and difference infrequency of two JJY.
Acknowledgement: We would like to thank A. Yoshikawa, T. Uozumi and S. Abe, Kyushu University, Fukuoka and T. Ohno,
Hoshinomura astronomical observatory, Fukushima, for cooperating LF radio observation.

Keywords: lightning discharge, subionospheric perturbation, dual frequency observation

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PEM27-P03

Room:Convention Hall

Time:May 26 18:15-19:30

Spectral analysis of ionospheric and atmospheric perturbations associated with typhoons
using HFD and microbarometer
HIRABAYASHI, Shinichiro1∗ ; NAKATA, Hiroyuki1 ; TAKANO, Toshiaki1 ; TOMIZAWA, Ichiro2
1

Graduate School of Engineering, Chiba University, 2 Center for Space Science and Radio Engineering

It is reported that ionospheric perturbations are observed by extreme weather conditions such as tornadoes and typhoons, andthey cause ionospheric disturbances. However, the features and propagation characteristics of atmospheric waves is still unclear.
We examined atmospheric waves caused by typhoons, using HF doppler (HFD), which is maintained by The University ofElectro-Communications, and microbarometer located at Mineyama, Kyoto prefecture. In this study, HFD receiver data for 5006
kHz observed at Sugadaira is used. Because of unstable ionosphere in the nighttime, we examined HFD data from 7:00 to 18:00.
Details of typhoons, path, barometric pressure, and wind speed, are provided by Digital Typhoon, managed by National Instituteof Informatics. Here, we give a brief description of Typhoon No.26 in 2013. This typhoon passed Japan in 2013/10/15 ˜10/17.
It was closest to the Sugadaira observation point on 10/16. From dynamic spectrum of HFD data, it is found that perturbationsof spectral intensity at the frequency under 5 mHz were observed in these 3 days even though Typhoon No.26 didn’t get closed
to Japan. On the other hand, spectral intensity of perturbations were enhanced at the frequency from 5 mHz up to 40mHz when
Typhoon No.26 got closed to Japan. Simultaneously, a perturbation of doppler shift was observed whose amplitude is 0.2 Hz.
Spectral intensity on microbarometer data also tended to be strong at the frequency from 5 mHz up to 50 mHz. Then we also
examined temporal variations of spectral intensity at 4 mHz and 30 mHz, comparing them with the distance between Sugadairaobservation point and the center of Typhoon No.26, and with wind velocity at Chichibu, which is the nearest observatory to thereflection point. Data of wind velocity was provided by AMeDAS, maintained by Japan Meteorological Agency. As a result,when Typhoon No.26 was approaching Japan, the spectral intensity of the perturbations at 30 mHz was clearly enhanced, but
not at 4mHz. Therefore, it is clear that typhoons seem to affect spectral intensity at frequency higher than 5mHz. The spectral
intensity reaches its maximum when the distance between Sugadaira and the center of Typhoon No.26 became the shortest. At
this moment the wind velocity at Chichibu became the strongest.
Keywords: Typhoons, ionosphere, atmosphere, microbarometer, HFD

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PEM27-P04

Room:Convention Hall

Time:May 26 18:15-19:30

Origin of small-scale field-aligned currents as observed by SWARM above the ionospherein middle and low latitudes
AOYAMA, Tadashi1∗ ; IYEMORI, Toshihiko2 ; NAKANISHI, Kunihito1
1Graduate School of Science, Kyoto University, 2 Data Analysis Center for Geomagnetism and Space Magnetism, Graduate
School of Science, Kyoto Univers
We analyzed magnetic field data obtained by the Swarm satellites launched on 22 November 2013, and confirmed that the
short-period(10˜40 s) and small-amplitude scaled(0.1˜5 nT) magnetic fluctuations observed in middle and low latitudes are the
manifestation of small-scale field-aligned current structure (Iyemori et al., GRL, 2015). Because of the characteristics of geographical and seasonal dependence of their amplitude obtained by analysis of the CHAMP satellite magnetic field data (Nakanishi
et al., EPS, 2014), we interpret these results as the indication of field-aligned currents generated by dynamo action in the ionospheric E-layer. We assume that the dynamos are caused by the acoustic waves generated by the lower atmospheric disturbances.
In this presentation, we show the evidence of the above interpretation by comparing the meteorological data with the magnetic
fluctuations, and estimate in which hemisphere, i.e., in north or south hemisphere, the origin of the dynamo exists from a comparison of spectral indices of the small magnetic fluctuations above typhoons in 2014.
Keywords: field-aligned current, ionospheric dynamo, atmospheric gravity wave, acoustic gravity wave, swarm satellite, typhoon

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PEM27-P05

Room:Convention Hall

Time:May 26 18:15-19:30

The verification of the small spatial structure of field aligned currents over the Brazilian
Anomaly
NAKANISHI, Kunihito1∗ ; IYEMORI, Toshihiko1 ; AOYAMA, Tadashi1
1Department of Geophysics, Graduate School of Science, Kyoto University

Nakanishi et al. (2014), using the magnetic data observed by the CHAMP satellite through high-pass filter with cutoff periodaround 40 seconds, show the ubiquitous existence of small scale (1-5 nT) magnetic fluctuations with period around a few tens
seconds along the satellite orbit in middle and low latitudes. The results of analysis show the difference in the dependence of theamplitude and period on latitude between the magnetic fluctuations over the Brazilian Anomaly and the other region. That is, as
the satellite approaches the dip equator, the period and amplitude get longer and smaller, respectively over the other region; on
the other hand, over the Brazilian Anomaly, the period doesn’t get longer and the amplitude doesn’t get smaller or rather getslarger respectively. Another characteristics of the magnetic fluctuations over the Brazilian Anomaly are similar to those over otherregions. That is, the magnetic fluctuations are perpendicular to the geomagnetic field; the amplitude on the dayside is much larger
than that on the nightside, which shows high correlation between the amplitude and the ionospheric conductivities in E-layer
with respect to local time; the amplitude has the geomagnetic conjugacy in general; almost no dependence on both geomagnetic
activity and the solar wind parameters is found; the global distribution of the amplitude has clear seasonal dependence with thegeographical characteristics.
They, putting importance on the dependence of the amplitude and period on latitude seen over the other region, suggest that theabove characteristics can be interpreted as the spatial structure of small scale ( 200 ? 300 km ) field-aligned currents generated
by the ionospheric dynamo driven by atmospheric gravity waves (acoustic mode or inertial mode) propagating from the lower
atmosphere. The dependence of the amplitude and period on latitude can be explained in the following way. With use of dipole
model, the spatial scale of the field aligned current is traced to the satellite altitude along the main magnetic field. The scale atthe satellite altitude gets larger as latitude decreases to the dip equator. Over the dip equator, the scale gets larger than a scalecorresponding to the cutoff period and the amplitude gets attenuated.
This time we verify that the magnetic fluctuations over the Brazilian Anomaly have the same generation mechanism with thoseover the different region and especially show the possibility that the different characteristic can be explained by the above model.
That is, as the geomagnetic field leans to the East-West direction over the Brazilian Anomaly, by trace along the magnetic field,
the latitudinal scale doesn’t get larger than the scale corresponding to the cutoff period comparatively even over dip equator,
therefore, the amplitude doesn’t get smaller comparatively.
The possibility shows that we can study the objective magnetic fluctuations over all the regions in middle and low latitudes
including the Brazilian Anomaly.

Keywords: spatial structure of field aligned currents, middle and low latitudes, the CHAMP satellite, the SWARM satellite,
atmospheric gravity wave, the Brazilian Anomaly

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PEM27-P06

Room:Convention Hall

Time:May 26 18:15-19:30

The relationship between ionospheric disturbances detected by HFD and ground perturbations associated with earthquakes
TAKABOSHI, Kazuto1∗ ; NAKATA, Hiroyuki1 ; TAKANO, Toshiaki1 ; TOMIZAWA, Ichiro2 ; NAGAO, Hiromichi3
1

Graduate shool of Engineering, Chiba University, 2 Center for Space Science and Radio Engineering, 3 Earthquake ResearchInstitute, The University of Tokyo
Many studies have reported that ionospheric disturbances occur after giant earthquakes. One of the causes is the acoustic wave
excited by surface waves propagated on the ground from the epicenter. In this study, we compared the ionospheric vertical drift
velocity calculated from HF Doppler (HFD) observation and vertical ground motions recorded at seismometer directly beneaththe reflection point of the HFD radiowave in order to elucidate relationships between them. The HF Doppler observation isenable to detect ionospheric disturbances since this can observe ionospheric vertical drift from Doppler shift of HF radiowaves
transmitted from the Chofu campus of The Univercity of Electro-Communications. In this study, using Doppler shift data for
5006 kHz, ionospheric disturbances associated with earthquakes are detected. To obtain accurate vertical drifts, we determinedreflection altitudes of radiowave from ionogram data (Kokubunji) using POLAN (ionospheric density profile calculation software) . For seismometer data, we used 2 types of seismic networks installed by NIED, Storong-motion Seismograph Networks(K-NET,KiK-net) and Broadband Seismograph Network (F-net) .
We examined the correlation of the maximum values of ionospheric vertical drift velocity and vertical velocity of ground motion for 30 events (M≥6, 2003˜2013) . HFD observatories are Sugadaira, Oarai, and Iitate. The closest seismomete from eachreflection points were selected.
As for Sugadaira observatory (20 events) , ionospheric velocity tends to increase in proportion to the square root of the ground
velocity regardless of types of seismometers. In the other two observatories (Oarai, Iitate), ionospheric velocities are not proportional to square root of the ground perturbations. This is because sufficient events are not supplied (6˜12 events) in theseobservatories. However, the ionospheric vertical velocity increases with the ground velocity. If the numbers of the events arelarger, the correlations of these observatories would be the same as the result of Sugadaira.
Keywords: ionosphere, HFD, earthquake, acoustic wave, seismometer, ground perturbations

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PEM27-P07

Room:Convention Hall

Time:May 26 18:15-19:30

Simulation Results for the Ionospheric Density Disturbances Triggered by Earthquake
Rayleigh Waves
CHEN, Chia-hung1∗ ; MATSUMURA, Mitsuru2 ; LIN, Charles1 ; SAITO, Akinori3 ; LIU, Jann-yenq4
1

Department of Earth Sciences, National Cheng Kung University, Taiwan, 2 National Institute of Polar Research, 3 Department ofGeophysics, Graduate School of Science, Kyoto University, 4 Institute of Space Science, National Central University, Taiwan
During the great earthquake event of M9.0 Tohoku earthquake on 11 March 2011 in Japan, previous studies detected the horizontal wave structure of ionospheric total electron content (TEC) disturbances by a dense ground-based GPS receiver network.
These results suggested that the ionospheric TEC disturbances could be caused by the earthquake-triggered seismic surface,
acoustic-gravity, and tsunami waves, which are distinguished by the different propagation velocities, durations, and periods. In
order to further investigate the vertical coupling effect for the ionospheric plasma density disturbances, this study employed athree-dimensional, non-linear, compressible numerical model. This model simulated the disturbances of neutral mass densities
from the surface to lower, upper atmosphere and the ionosphere, by specifying the surface displacement triggered by the earthquake, such as the rayleigh waves, at the model lower boundary. The results show that the TEC disturbances have two types ofthe propagation waves, first horizontal waves and slow co-centric waves. These might be caused by the neutral wind dynamo
effect and the ion-neutral collision along the magnetic field.
Keywords: Earthquake, Rayleigh wave, Ionosphere, Plasma density disturbance

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PEM27-P08

Room:Convention Hall

Time:May 26 18:15-19:30

Comparison between the ionospheric holes between inland earthquakes and subduction
earthquakes with tsunami.
KANAYA, Tatsuya1∗ ; KAMOGAWA, Masashi1
1Dpt. of Phys., Tokyo Gakugei Univ.

We investigate the ionospheric holes generated by two inland earthquake and two subduction earthquakes with tsunami ofwhich magnitudes are similar, using data of GPS total electron content. For the comparison, the ionospheric hole clearly appeared
only in the subduction earthquakes. From our interpretation, this is due to the difference of the initial conditions to excite theacoustic waves.
Keywords: Ionospheric hole, Inland earthquake, Tsunami

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PEM27-P09

Room:Convention Hall

Time:May 26 18:15-19:30

OBSERVATION OF METEOR SHOWERS IN 2014 - 2015 BY 5CH HRO-IF ANDEVALUATION OF SYSTEMS AT KOCHI UNIVERSITY OF TECHNOLOGYMIZUMOTO, Satoshi1∗
1

Kochi Tech of Univ.

Introduction: Ham-band Radio meteor Observation (HRO) has an advantage of 24-hour continuous data-detection. In Kochi
University of Technology (KUT), 5 channel HRO-interferometer (HRO-IF) was developed in 2009 and has been observing themeteor appearance position of every meteor echo. We operated an automatic meteor observation system that automatically showsobservational results on Web in quasi-real time for about two years until 2011 (Noguchi, 2009). In addition, we have developed asystem of meteor trajectory measurement by multiple-sites observation with GPS time keeping and the 5ch HRO-IF (Yamasaki,2012). In 2012, an HRO observation with a calibrating system which could regularly observe the absolute strength of the meteor
echo was developed, thus the plasma density of each meteor echo was precisely determined (Yamato, 2013). We will reportobservation facilities, equipments, the future prospects and latest observation result.
Meteor observation by 5ch HRO-IF: In KUT, we started 6 direction HRO in 2003. We performed the basic development of the
3ch HRO-IF from 2005 to three years (Horiuchi, 2005; Okamoto, 2005) and obtained an arrival angle of each meteor echo fromthe phase difference of three antennas, calculating the approximate meteor appearance position (Hamaguchi, 2006; Noguchi,2007). The 3ch HRO-IF is limited in positional accuracy for the angle of arrival obtained from the phase difference. In order tosolve this problem, we developed the 5ch HRO-IF as the improved version in 2009, realizing the automatic meteor observation
for two years in KUT (Noguchi, 2009). Since high time resolution is needed for interferometer, we calculate phase difference atevery 0.1 s, synchronizing the 5 channel input signal to an AD board with 1 PPS (Pulse Per Second) signal provided by a GPS
receiver every 1 s. We observed Camelopardalis meteor shower (May, 2014) and Daytime Arietids meteor shower (June, 2014)by using these equipments.
Meteor shower observation result in 2014 - 2015: We observed meteor showers of Camelopardalis, Daytime Arietids andLeonids 2014 by the KUT 5ch HRO-IF. We tried calculate trajectory vector of each meteor echo by a multisite observation ofGeminids 2014 and Quadrantids 2015 meteor showers. The multisite observation system was developed with the other two HRO
sits in addition to the KUT 5ch-IF. Preliminary result of the multisite observation was obtained and the system performance was
evaluated with trouble shooting process.
Summary: We performed the KUT 5ch HRO-IF as a forward scattering meteor radar system continuously with some verifications of accuracy that is important to reveal meteor showers structures (e.g. Geminids). However, it is necessary to realize
calculation of meteor trajectory information by the multiple-sites observation to obtain precise parameters of the meteor showers
such as the suddenly observed Camelopardalid 2014 meteor shower. Therefore, we will have to develop an improved version of
the HRO-IF observation system as a permanent automatic data transmission with acquiring observation data from multiple sites.
We tried multisite observation of Geminids 2014 and Quadrantids 2015 meteor showers with evaluating the system performanceand trouble shooting process. In this paper, we will report the current status of the KUT 5ch HRO-IF system with recent observational results in 2014 - 2015 and outlook for the future.

Keywords: Meteor radio observations, Radio interferometer, Multisite observations

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PEM27-P10

Room:Convention Hall

Time:May 26 18:15-19:30

Large-scale structure and continuation of intense Es around the Kyusyu-Okinawa by VHF
long-distance propagation
YANAGISAWA, Shinya1∗ ; TOMIZAWA, Ichiro1 ; YAMAMOTO, Atsushi2
1

Center for Space Science and Radio Engineering, 2 Maritime Science and Technology, Japan Coast Guard Academy

We have been observing VHF long-distance propagations reflected by intense sporadic-E (Es) both at Kure and at Chofu[1]. It has shown that intense Es may have a very long and thin structure [2]. In this report, we describe the large structure
and the moving characteristic of three intense Es observed around the Kyushu-Okinawa area on May 11, 2014 and September
14, 2013 and July 1, 2014. Since these three events were observed in the same area, it’s suitable to compare the structure andcharacteristics.
(1) The speed of Es by VOR around 17:00 JST on September 14, 2013 was about 40 m/s and the length of the intense Es
observed was about 300 km moving in southeast. The width of the Es was 7˜20 km which was much smaller than the length,
but the west-portion became expand to 120 km, and the moving speed and the direction were different from the east-portion.
Therefore, the whole structures were presumed to be during the observation period bending around the center. Additional thewest-portion became thick with progress, but the east-portion did not showing change. Moreover, the duration times of the Es
were more than 2 hours.
(2) The Es observed at around 19˜21:00 JST May 11, 2014, had two frontal structures moving in the same northwestward
direction. But the two fronts had the moving speed of 50˜60 m/s, the length fronts of 300˜400 km, and the variable width of 5˜80
km, the duration time were about 1 hour.
(3) The Es observed at around 10˜11:00 JST July 1, 2014, had two frontal structures moving in the same northwestward
direction. While moving 2 structures with speed different in about 50 m/s and about 150 m/s big as a point different from (2),and it intersected. The length of the structure was same as about 380 km and about 300 km mostly but different from 7˜35km
and 55˜180 km in the width of the structure big like (2). Both of 2 were about 1 hour in duration.
These three intense Es observed in the same area had the structure length of 300˜400km equally, but the Es structure andmoving speed were different. (1) was the southeast for the movement direction, but (2) and (3) were the reverse northwestward.
Moreover (1) could continue high electronic density structure for about 2 hours, but only half of about 1 hour of (1) could
continue (2) and (3). As these results, intense Es can be presumed that can move maintain the slender structure for about 1-2
hours.
In poster session, we will describe the comparative results, such as the moving characteristic of Es, the feature and structure,
are reported in detail.
[1]Takuya Yamahata, Ichirou Tomizawa, Atsushi Yamamoto: Broader-based Es structure observation system development by
VHF belt long distance propagation reception, SGEPSS, B005-P038, 2012.
[2]Ichirou Tomizawa, Koutarou Hujii : HF wave reflection propagation model by the shape of a wave face Es, JPGU, P-EM2901, 2013.

Keywords: Ionosphere, Sporadic E layer, Large-scale structure

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PEM27-P11

Room:Convention Hall

Time:May 26 18:15-19:30

Derivation of shape of cross-section of frontal sporadic E by the HF Doppler spectral
analysis
OHTA, Hiroki1∗ ; TOMIZAWA, Ichiro1
1

Center for Space Science and Radio Engineering ,UECAs for shape of cross-section of frontal sporadic E(Es), it has been revealed that had a shape of thin cylindrical structure bya past study [1]. However, there are no observation data about the shape of cross-section along Es front concerning we havedeveloped a new method of analysis HF Doppler spectrum multi-state network in Kanto with high resolution.
At first I observe shape of cross-section of frontal Es passing HFD middle reflection point of Kanto and demand three dimensions of details data of the electric field strength every Doppler shift frequency at the near midway point passage time. We areable to consider the change to be the incidence angle dependence of the equivalence of value dispersion cross section when an
radio wave was incident on a slim Es shape of cross-section from the lower part in time for field strength that cut and brought
down these data every constant frequency. Because the baseline halfway point between each transmission and reception points
are different, We can estimate cross-section of frontal Es reflection surface finely. I find a movement direction and the speed offrontal Es by performing this analysis at the many observation point and derive the sectional structure of the reflection wholeshape of cross-section of frontal Es in detail.
A change really demands an average change from the electric field strength graph which cut and brought down observation
data in the frequency direction by a quadratic equation fitting by the least-squares method because it is difficult to greatly analyze
it directly. We found width based on this average change at the biggest strength every the Doppler shift frequency and the time, 3dB time width. We found the width of cross-section of frontal Es from the product of 3 dB time width and the horizontal mobility
speed, and the irregularity of shape of cross-section from the biggest strength and the time.
I applied the above mentioned method of analysis and checked the frontal Es which occurred at 23:00 JST on July 23, 2009
in detail. Shape of cross-section of frontal Es which advanced in 102 m/s, the southwestern direction, and the width of shapeof cross-section was found with approximately 12 km. This shape of cross-section of frontal Es knew that structure and theasymmetry structure that there were not only one simple mountain-formed sectional structure but also two mountains existed
when I looked at the shape of cross-section of the Es in resolving power of Fresnel zone approximately 4 km.
From the above results, I knew that I could derive shape of cross-section of frontal Es on the scale of the Fresnel zone bychecking HF Doppler spectrum in detail at each observation point. I derive a regularity of the structure of shape of cross-sectionof frontal Es by performing this analysis for more frontal Es and can expect that I understand deeply to an atmosphere change tobe concerned with Es generation.

[1]Ichiro Tomizawa and Kotaro Fujii: HF propagation model reflected by frontal Es, JPGU 2013, PEM29-01, 2013.5.
Keywords: ionosphere, HF Doppler, Sporadic E

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PEM27-P12

Room:Convention Hall

Time:May 26 18:15-19:30

Examination of the Es propagation model of ITU-R based on VOR long distance propagation and the observation of ionosonde
NITTA, Takuya1∗ ; TOMIZAWA, Ichiro1 ; YAMAMOTO, Atsushi2 ; SHINJI, Saitoh3
1

Center for Space Science and Radio Engineering ,UEC, 2 Japan Coast Guard Academy, 3 Electronic Navigation Research Institute
The University of Electro-Communications observe Very High Frequency Electric wave Reflected in Sporadic E layer in Chofu
and Kure. It is necessary to check electron density structure in a wide area to examine it whether a long-distance propagation
wave by a strong Es reflection pro-VHF propagation (GBAS-VDB) is not beyond interference permissible level. In the Es propagation model of ITU-R based on the observation until
the 1970s, expression of relations of the Es reflection ionosphere reflection decrement quantity is guaranteed only to Electric
wave Reflected in Sporadic E layer to 80MHz. In this lecture, I express the result about whether it is possible to apply data of theionosphere reflection decrement quantity observed from VOR observation of frequency around 110MHz and NICT verticality
critical point frequency foEs data of the middle reflection point neighborhood to Es propagation model type of ITU-R.
In from May 1, 2014 to September 30, I observed an electric wave of the VOR transmission station of Yoron Island (27.044N,
128.398) and Yonagunijima (24.457N, 122.998E) which the distance with Yamagawa (31.20N, 130.62E) and the VOR middle
reflection point was close in Kure (34.246N, 132.528E). I demanded Yamagawa perpendicular critical frequency foEs and ionosphere reflection decrement quantity for the use frequency and, from data of provided VOR reception electricity, performed thecomparison with the Es propagation model type of ITU-R. As a result, which is obtained from Kure VOR reception electricity is smaller than the Es propagation model of ITU-R and gives weaker value than real reception electricity. This goes down
assuming the Es reflection model that is bigger than Fresnel zone in the Es propagation model of ITU-R, and it is thought that
this is because it observes the Es in Fresnel zone domains by the VOR long distance propagation observation. The ionospherereflection decrement quantity between Kure and Yoron Island interval of surface of the earth propagation distance 893km has abigger bigger difference with the predicted value than Kure and Yonagunijima Island interval of surface of the earth propagation
distance 1427km. In addition, it becomes the slow degree of leaning in the VOR when I pay attention to a degree of leaningof ionosphere reflection decrement quantity for foEs and shows that an index to express the frequency dependence of the Es
propagation model of ITU-R is too big. As a result, it is necessary for the propagation model type of ITU-R in frequency around
110MHz to perform a review. I increase the number of the examination lines and am going to examine an Es propagation modeltype of ITU-R at around 110MHz in detail in future.
References[1] Takuya Yamahata, Ichiro Tomizawa, Atsushi Yamamoto: Wide area Es structure observation system development by the
VHF Zone long distance propagation reception, SGEPSS, B005-P038, 2012.
[2] Shinji Saitou, Ichiro Tomizawa, Atsushi Yamamoto: Examination of the influence of the VOR long distance propagation by
the sporadic E on GBAS-VDB, communication engineering technology research report, vol. 114, SANE2014-125, pp113-118,
2015.
[3] K. Miya and T. Sasaki: Characteristics of ionospheric Es propagation and calculation of Es signal strength, Radio Sci.,
vol.1, pp.99-108, 1966.
[4] ITU-R:Recommendation of ITU-R, Method for calculating sporadic-E field strength, Rec.ITU-R P.534-4,1999.

Keywords: ionosphere

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PEM27-P13

Room:Convention Hall

Time:May 26 18:15-19:30

Estimation of spatial structure of sporadic E layer observed by S-310-40 rocket with 2dimentional FDTD simulations
MIYAKE, Taketoshi1∗ ; INOUE, Hironori1 ; ISHISAKA, Keigo1
1

Toyama Prefectural University
We developed a 2-dimensional FDTD simulation code
which can treat wave propagations in magnetized plasma.
According to sounding rocket experiments,
we can only obtain altitude profile of wave intensity,
usually magnetic field intensity.
In this study, therefore, we are going to estimate spatial structure of sporadic E layer
in the lower ionosphere by analyzing the altitude profile of the magnetic field intensities.
We compared simulation results and observation results obtained by S-310-40 sounding rocket,
but were not able to identify spatial structure of the sporadic E layer.
This is because the scale of the spatial structure of the sporadic E layer
assumed in the simulation was inappropriate.
We are going to perform 2-dimensional FDTD simulations with different spatial scales of the sporadic E layer,
and investigate the influence that a scale of the space structure gives electric wave propagation.
Then, we will identify spatial structure of the sporadic E layer observed by S-310-40 sounding rocket
from the altitude profile of the magnetic field.

Keywords: Sporadic E layer, spatial structure, 2D FDTD simulation

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PEM27-P14

Room:Convention Hall

Time:May 26 18:15-19:30

Improvement of an estimation method of the electron density profile in the lower ionosphere with time domain Full wave
MIYAKE, Taketoshi1∗ ; MORIYAMA, Hiroaki1 ; ASHIHARA, Yuki2 ; MURAYAMA, Yasuhiro3 ; KAWAMURA, Seiji3
1

Toyama Prefectural University, 2 Nara National College of Technology, 3 National Institute of Information and Communications
Technology
We are going to simulate the observation process of the present MF radar systemwith the time domain Full wave method,and investigate the observation method with which
we can obtain the precise electron density profile in the lower ionosphere.
One of the general methods to estimate the electron density in the present MF radar systemis the differential absorption experiment (DAE) method.
The DAE method is a technique to estimate the electron density fromthe differential amount between the left and the right polarized waves
reflected from the lower ionosphere.
We simulated the MF radar with time domain Full wave analysis and examined the DAE method.
We improved the DAE method by using appropriate parameters automatically,and succeeded to estimate more accurate electron density profiles in the lower ionosphere.
In the present improved DAE method, however,
we can only find appropriate parameters in the case thatthe electron density increases with increase of the altitude.
Therefore, we are going to improve the DAE method, which is available in any case.
Keywords: Ionospheric D region, MF Radar, Full-wave method, DAE method

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PEM27-P15

Room:Convention Hall

Time:May 26 18:15-19:30

Analysis of Propagation Characteristics of Radio Wave by S-520-29 Sounding Rocket
ITAYA, Keita1∗ ; ISHISAKA, Keigo1 ; ASHIHARA, Yuki2 ; KUMAMOTO, Atsushi3 ; ABE, Takumi4 ;KURIHARA, Junichi5
1

Toyama Prefectural University, 2 Department of Electrical Engineering, Nara National College of Technology, 3 Departmentof Geophysics, Graduate School of Science, Tohoku University, 4 Japan Aerospace Exploration Agency Institute of Space andAstronautical Science Department of Solar, 5 Graduate School of Science, Hokkaido University
S-520-29 sounding rocket experiments was carried out in Uchinoura Space Center on August 17, 2014. The purpose of thissounding rocket experiments is observation of sporadic E layer that appears in the lower ionosphere at near 100km. Therefore,
the experiments was carried out using three methods. The first method is an optical method that observe light of metal ion emitted
by the resonance scattering in sporadic E layer using the imager. The second is a method of using radio waves that receive the
LF/MF band radio waves transmitted from the ground to rocket. The third is a method that measuring the electron density inthe vicinity of sounding rocket using the fast Langmuir probe and the impedance probe. In this presentation, we explain the
preliminary report of radio waves observations and radio waves propagation characteristics using frequency analysis of S-520-29
sounding rocket experiment. This rocket was equipped with LF/MF band radio receiver for observation of characteristics of
LF/MF band radio waves propagation, and observe the LF/MF band radio waves in rocket flight. Antenna of LF/MF band radio
receiver is composed of three axis loop antenna. LF/MF band radio receiver receives three radio waves of 873kHz (JOGB),
666kHz (JOBK), 60kHz (JJY) from the ground. 873kHz and 60kHz radio waves are coming from north side of the rocket,
666kHz radio waves are coming from the east side to the trajectory of the rocket. It is possible to estimates the position andsize of the high electron density region in the sporadic E layer by analysis radio waves propagation characteristics using radio
waves come from different directions. In the sounding rocket experiment, LMR was working properly. We have completed theobservation of radio wave intensity. We analyze the observation results using a Doppler shift calculations by frequency analysis.
Radio waves received by the sounding rocket undergoes a Doppler shift by polarization and direction of rocket spin and magnetic
field of the earth. Radio waves received by the sounding rocket was separated into characteristics waves using frequency analysis.
Then we calculate the Doppler shift from the separated data. Finally, this study estimate the electron density by using Doppler
shift and the equation of booker. As a result, 873kHz, 666kHz radio waves are reflected by the ionosphere. 60kHz radio wave waspropagated to maximum altitude of sounding rocket after it converted into whistler mode. Then, this study was able to estimate
the altitude distribution of electron density by using the Doppler shift. In this study, we explain the reports of LMR observations
and characteristics of radio waves propagation by frequency analysis by S-520-29 sounding rocket experiment.
Keywords: sounding rocket, radio wave propagations, Doppler shift, sporadic E layer

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PEM27-P16

Room:Convention Hall

Time:May 26 18:15-19:30

Velocity distribution of electrons generating plasma waves around the wake of an ionospheric sounding rocket
ENDO, Ken1∗ ; KUMAMOTO, Atsushi1 ; KATOH, Yuto1
1

Department of Geophysics, Graduate School of Science, Tohoku University

When a body moves in plasma at supersonic velocities, a rarefied plasma region called ’plasma wake’ is formed behind the
body. Wakes can develop behind a solar system body immersed in solar-wind plasma as well as behind spacecraft such as satellites and ionospheric sounding rockets.
Plasma waves around the rocket wake have been suggested by the observational results from previous rocket experiments,
while there are also several studies which reported plasma waves around the wakes of a satellite and of the moon. In the S520-26 rocket experiment (apex: 298 km), carried out in Japan at dawn of January 12, 2012, three kinds of plasma waves wereidentified (hereafter denoted Group-A,B, and C). We concluded that they are electrostatic electron cyclotron harmonic (ESCH)
waves or upper hybrid resonance (UHR) mode waves (Group-A waves), and whistler mode waves (Group-B and Group-C waves).
They have spin-phase dependence in characteristic manners.
Meanwhile, it was found that Group-A waves were also observed in the S-520-23 rocket experiment (apex: 279 km), which
was performed in Japan at dusk of September 2, 2007, and that their spin-phase dependence is nearly the same with that of theGroup-A waves observed in the S-520-26 rocket experiment.
We performed numerical calculations of plasma dispersion relations by assuming anisotropic velocity distribution functions
such as electron beam and temperature anisotropy. As a result, positive linear growth rates have been obtained in the wave number and frequency ranges of UHR mode waves and ESCH waves in addition to electrostatic whistler mode waves. Accordingly,
there have to be electrons with some anisotropic velocity distribution functions which are equivalent to those we assumed in thecalculations. However, we have to clarify what kind of velocity distribution can be generated around the actual wake through theinteraction between a sounding rocket and ionopsheric plasma.
Singh et al. (1987) performed a one-dimensional simulation of plasma entering a void region from the two sides using a
Vlasov-Poisson code. They found counterstreaming electron beams in the very near wake. However, their study concentrates onelectrons on the wake axis and does not indicate distribution functions in other areas. Besides, temperature anisotropy could not
be treated in their simulation because it was performed in one dimension in velocity space.
In order to investigate inhomogeneity of electron distribution functions around the rocket wake, we are developing a VlasovPoisson code with one-dimensional space and two-dimensional velocity space, which is redesigned from the simulation codeused in Singh et al. (1987). In this simulation, we deal with cases that electrons and ions are filling in a void space. The time
evolution can be understood as spatial distribution along the wake axis. The direction of one-dimensional space is along thegeomagnetic fields, along which electrons and ions can move easily. The size of space is 10 m, which is divided into 1024 grids
in the calculation.
In this presentation, we clarify the frequency range and spatial distribution of the plasma waves around the wake based on
the analyses of S-520-26 and S-520-23 rocket experiment data. We also discuss the velocity distribution of the electrons which
can generate the plasma waves as observed. In addition, we report the results of our simulation for investigating the velocity
distribution of electrons around the wake.
Keywords: wake, plasma wave, sounding rocket, ionosphere

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PEM27-P17

Room:Convention Hall

Time:May 26 18:15-19:30

Characteristic feature of plasma irregularity obtained in ICI sounding rocket campaign
ABE, Takumi1∗ ; MOEN, Joran2
1

Japan Aerospace Exploration Agency, 2 University of Oslo

ICI-3 (Investigation of Cusp Irregularities) campaign was conducted in December 2011, to study a better description of plasma
instabilities and wave phenomena related to Reversed Flow Events (RFEs) in the cusp ionosphere. In this campaign, sounding
rocket was launched at Ny-Alesund in Svalbard, and intercepted the dayside cusp aurora region as expected. Among science
instruments onboard, a purpose of Fixed Bias Probe (FBP) is to measure electron current incident to its spherical probe with hightime resolution for investigating plasma irregularity with a spatial scale from 1 m to 100 m. The FBP successively identified
existence of the small-scale electron density irregularity during the flight.
Power spectrum analysis was applied to the incident electron current, which is basically proportional to the electron density,with an interest in understanding characteristic feature of the spatial scale in the irregularity. In fact, the data obtained in thiscampaign are appropriate to investigate altitudinal variation of the frequency characteristics because the rocket was staying almostin the irregularity region through its flight.
As a result of spectrum analysis of the electron density variation, it is clearly found that spectral power with 10 meter scale
increases with altitude. However, it should be noted that spectral power tends to increase with the background density if theirregularity is contained at a constant rate in the background density. Therefore, spectral amplitude normalized by the backgrounddensity was used to investigate the altitudinal dependence. Our analysis indicates that normalized amplitude of the density
irregularity with 1-10 m scale is most significant at altitudes between 100 and 150 km, while the one with 100 m scale is almost
constant independently of altitude. In particular, it is noticeable that the amplitude of electron density irregularity has a small
local maximum in the frequency of 100-200 Hz (corresponds to decameter spatial scale) at ˜100 km altitude. Such feature is notfound at other altitudes. The electron density irregularity with such a scale can be a target of HF backscatter radar echoes.
We will discuss altitudinal variation of the density irregularity in more detail.

Keywords: Sounding rocket, plasma irregularity, ionosphere, Cusp, electron density

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PEM27-P18

Room:Convention Hall

Time:May 26 18:15-19:30

Space structure of Es layer observed by Langmuir probe and a new analysis method
SAKAMOTO, Yumika1∗ ; ABE, Takumi2 ; MIYAKE, Wataru1
1

Department of Aeronautics and Astronautics Graduate School of engineering, Tokai University, 2 Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency
The sporadic E layer has been studied for a long time, and wind-shear theory is generally accepted about its generation mechanism. The theory explains an accumulation process of the electron density, but hardly gives information on thermal energy
budget inside the layer. A great number of observations have been reported about the electron density structure in the sporadic
E layer, but few information on the electron temperature are available, and therefore the accurate measurement is expected to
conduct on the sounding rocket. In general, since a velocity of the sounding rocket is very high, it is difficult to get high special
resolution data on the density structure of the sporadic E layer in the vertical direction. Therefore, it is necessary to find a new
idea to estimate electron temperature and electron density in high-time resolution to understand the small scale structure of thesporadic E layer.
The sounding rocket ”S-520-29” was launched from Uchinoura Space Center at 19:10 on August 17, 2014. The purpose ofthis experiment is to elucidate spatial structure of sporadic E layer in the lower ionosphere. Langmuir probe was installed as
one of the probes for direct measurements. In some current-voltage characteristics obtained by the Langmuir probe during thisexperiment, it was noted that the current variation with the bias voltage showed unusual behavior which suggests significant
gradient in the electron density inside the sporadic E layer. In such a case, it is not possible to estimate electron density andelectron temperature by using the conventional method.
In this study, we suggest a new analysis method to enable accurate estimation of the electron temperature and density, evenwhen electron density is rapidly changed. It becomes possible to estimate the temperature and density in a time interval shorter
than a period of the voltage sweep, because the probe current are interpolated by using adjacent data.
In this presentation, we report the small scale density structure and vertical thickness of the sporadic E layer estimated byadopting the new method, and validity of the current interpolation.

Keywords: E layer, Langmuir probe, sounding rocket

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PEM27-P19

Room:Convention Hall

Time:May 26 18:15-19:30

Analysis of DC electric field in ionosphere by S-520-26 sounding rocket
ISHISAKA, Keigo1∗ ; YAMAMOTO, Mamoru2 ; YOKOYAMA, Tatsuhiro3 ; ABE, Takumi4 ; WATANABE, Shigeto5
1

Toyama Prefectural University, 2 RISH, Kyoto University, 3 NICT, 4 ISAS, 5 Hokkaido Univeristy

S-520-26 sounding rocket experiment was carried out at Uchinoura Space Center (USC) in Japan at 5:51 JST on 12 January,
2012. The purpose of this experiment is the investigation of the bonding process between the atmospheres and the plasma in thethermosphere. S-520-26 sounding rocket reached to an altitude of 298 km 278 seconds after a launch. The S-520-26 payload wasequipped with Electric Field Detector (EFD) with a two set of orthogonal double probes to measure both DC and AC less than
200 Hz electric fields in the spin plane of the payload by using the double probe method. One of the probes is the inflatable tube
structure antenna, called the ITA, with a length of 5 m (tip-to-tip). And ITA is very lightweight (12.5g per one boom). The ITA
extended and worked without any problems. It was the first successful use of an inflatable structure as a flight antenna. Anotherone is the ribbon antenna with a length of 2 m (tip-to-tip). The electrodes of two double probe antennas were used to gather
the potentials which were detected with high impedance pre-amplifier using the floating (unbiased) double probe technique.
The potential differences on the two main orthogonal axes were digitized using 16-bit analog-digital converter, sampled at 800
samples/sec with low pass filter at cut-off frequency of 200 Hz.
Results of measurements of DC electric fields by the EFD have the large sine waves that result from the payload rotation at the
spin period. The largest contribution to the electric field measurements by double probes moving through the ionosphere at midlatitudes is that due to the v X B fields created by their motion across the ambient magnetic field, where v is the rocket velocity
in the Earth-fixed reference frame and B is the ambient magnetic field. The sum of the squares of the two components represents
the magnitude of the DC electric field in the spin plane of the payload. These data reveal abrupt, large-scale variations which
can immediately be attributed to changes in the geophysical electric field since the v X B fields are slowly varying. The sumof the squares data also reveals contributions at the spin frequency and its harmonics. These contributions result primarily fromdistortions of the waveforms in the raw data. Then we obtained three components of natural DC electric fields by subtracting thev X B fields from raw data. As a result, the magnitude of DC electric field on a rocket orbit during the ascent was about 1mV/m,and the direction was for north-east.

Keywords: DC electric field, ionosphere, rocket experiment

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PEM27-P20

Room:Convention Hall

Time:May 26 18:15-19:30

Inter-annual variations of Nitric Oxide in the polar mesosphere observed by a millimeterwave radiometer at Syowa
UEMURA, Miku1 ; ISONO, Yasuko2 ; NAGAHAMA, Tomoo1∗ ; MIZUNO, Akira1 ; EJIRI, Mitsumu K.2 ;TSUTSUMI, Masaki2 ; NAKAMURA, Takuji2 ; MIYOSHI, Yoshizumi1
1

Solar-Terrestrial Environment Laboratory, Nagoya University, 2 National Institute of Polar Research

Recent observations revealed that the nitrogen oxides (NO,NO2) are increased in the lower thermosphere and the mesosphereand the upper stratosphere, when energetic particle precipitations associated with solar proton events or magnetic storms occurred(e.g. Lopez-Puertas et al. 2005),. To detect such the enhancement, we installed a millimeter-wave spectroscopic radiometer at
Syowa Station in Antarctica, and observation of the NO spectrum has been conducted since January 2012. The NO column
density derived from this observation shows a seasonal variation that the NO column density increases in winter. In winter, theobserved NO column density of 2014 is lower than 2012 and 2013.
To study reliability of millimeter wave spectral radiometer, we compared the NO column amount with the SOFIE sensor on
board AIM satellite. We picked observed data in the same magnetic latitude zone as the Syowa Station, and calculate an NO
column density. The NO column density observed at Syowa Station and SOFIE shows a same tendency. Further, we comparedmonth averaged NO column density, and found a good correlation. From this, the millimeter-wave spectral radiometer do uniform
observations, and decreasing of the NO column density in 2014 winter season is reliably phenomenon.
Next, we study about impact of variations of relativistic electron flux to NO column density in winter. We used the electron
flux data observed from POES satellites and calculated monthly integrated amount of the electron flux. The electron flux in the2014 is less than those of 2012 and 2013. In particular, this tendency is significant in a period between April and August in 2014.
From this, a lower amount of NO column density of 2014 winter may be caused by a low amount of relativistic electron flux.

Keywords: microwave spectroscopy, Nitric Oxide, MLT region, Energetic Particle Precipitation

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PEM27-P21

Room:Convention Hall

Time:May 26 18:15-19:30

An observation of sodium twilight airglow using a Fabry-Perot imager
SUZUKI, Hidehiko1∗ ; TAKAHASHI, Hideyuki2 ; TAGUCHI, Makoto2
1

Meiji university, 2 Rikkyo university

The mesosphere and lower thermosphere (MLT) region is thought as a key region to solve a mechanism of the global change inthe Earth’s atmospheric system. Atomic metal layers which are maintained by ablation of meteors in the MLT region are known
as a precious tracer to investigate chemistry and dynamics of the upper atmosphere [Williams, 2002]. For example, resonancescatter lidars tuned for wavelengths of various metal species are widely used to infer the winds and temperature in the MLT region[Plane, 2003]. However, there are still many ambiguities in knowledge about a horizontal structure and a seasonal variability ofthe metal layers. Therefore, a twilight airglow is focused on as a tracer to investigate horizontal structures of the metal layers
in the MLT region in this study. The twilight airglow is luminous phenomenon which is caused by a resonance scattering of
the metallic atoms in the MLT region illuminated by solar irradiance. This emission is effectively detectable in twilight time
under a suitable geometric condition among the Sun, the metal layers, and a ground-based observer [e.g. Chamberlein, 1961].
Unlike a resonance scattering lidar, an emission from a metallic atom layer occurs simultaneously in a horizontally spread area,
because a light source of the emission is solar irradiance in a case of twilight airglow. Thus, it is possible to deduce a horizontal
distribution of metallic atoms from twilight airglow observations by using a sensitive and narrow band imaging device with awide field of view. The Fabry-Perot interferometric imager (FPI) of the National Institute of Polar Research (NIPR) is one of
instruments which satisfy these requirements. In this study results of a test observation of sodium twilight airglow, which isone of the strongest emissions in twilight, using the FPI at NIPR are presented, and future possibilities for study of a horizontal
structure of metallic atom distribution in the MLT region using the FPI are discussed.
Keywords: twilight airglow, mesosphere, thermosphere, metallic layer, Fabry-Perot

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PEM27-P22

Room:Convention Hall

Time:May 26 18:15-19:30

An estimation of three-dimensional structures of airglow emission discontinuities using
images taken from ISS
SATO, Masato1∗ ; SAITO, Akinori1 ; AKIYA, Yusuke1 ; HOZUMI, Yuta1
1

Graduate School of Science, Kyoto University

Three-dimensional structures of airglow emission discontinuities were revealed using images taken by astronauts from International Space Station (ISS). Airglow layers over the Earth’s rim were captured by astronauts with a digital camera at night.
Because these images were for the visible-light range, Na 589nm and OI 557.7nm emissions 90km altitude were expected to
be dominant on these images. Two discontinuities on the airglow layers were observed on 16 October 2011 and 26 August
2014. They were observed from various viewing-angles during observing time 4m24s and 8m15s. Thus the three-dimensional
structures of the discontinuities were estimated from these series of images. It was found that the structures would be causedby splitting of two emission layers, Na and OI. It is also found that they extended over 700km in the east-west direction. We
estimated the altitude distributions of these emission layers’ intensity and their RGB ratio by using Abel function. From theground-based optical observation, mesospheric bore has been observed as an airglow discontinuity by terrestrial observation of
airglow. The observed discontinuities and the bores have similarities and differences. In the presentation, the three-dimensional
structures of the discontinuities will be reported, and their generation mechanism will be discussed in the comparison with thebore.
Keywords: airglow, mesospheric bore

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PEM27-P23

Room:Convention Hall

Time:May 26 18:15-19:30

New analysis of gravity wave in middle atmosphere by Rayleigh/Raman lidar at Syowa
station in Antarctica
KOGURE, Masaru1∗ ; NAKAMURA, Takuji2 ; EJIRI, Mitsumu K.2 ; NISHIYAMA, Takanori2 ; TSUTSUMI, Masaki2 ;TSUDA, Takuo3
1

Department of Polar Science, The Graduate University for Advanced Studies, 2 National Institute of Polar Research, Japan, 3 The
University of Electro- Communications

The gravity waves are generated in lower atmosphere, propagate upward and transfer momentum to the middle atmosphere.
It has been found that the gravity waves induce large scale meridional circulation and drive the middle atmosphere away fromradiative equilibrium [Lindzen, 1981; Holton, 1982; Matsuno, 1982]. However, we has not completely known the quantificationof gravity wave roles in the middle atmospheric circulation. In particular, it has not been found that the quantification of gravity
waves generated from convection (e.g. polar night jet). A Rayleigh/Raman lidar was installed in January 2011 at Syowa station,
Antarctica (69S, 40E). It has measured temperature profiled between approximately 8 and 70 km for more than 850 nights (before
the end of October in 2014).
We have analyzed the lidar data based on Duck et al. (2001) and Alexander et al. (2011). However, their analysis has a problem.
They estimated gravity waves’ temperature amplitude to be the value (T ′ ) that is difference between background temperature
and atmospheric temperature. Their analysis may underestimate the potential energy (Ep ) due to not consider the phase. To
solve the above problem, we calculated the value (Th ′ ) delaying 90 degree from T ′ phase to perform Hilbert transformation
on T ′ weighted by the square root of density, and defined gravity waves’ temperature amplitude as ((T ′ )2 +(Th ′ )2 )1/2 . In
this presentation, our analysis will be explained in detail.

Keywords: Stratsphere, Mesosphere, Middle atmosphere, gravity wave, Antarctica, Lidar

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PEM27-P24

Room:Convention Hall

Time:May 26 18:15-19:30

Measurements of Fe and Ca+ temperatures using by a frequency-tunable lidar
TSUDA, Takuo1∗ ; EJIRI, Mitsumu K.2 ; NISHIYAMA, Takanori2 ; ABO, Makoto3 ; KAWAHARA, Takuya4 ;NAKAMURA, Takuji2
1

The University of Electro-Communications, 2 National Institute of Polar Research, 3 Tokyo Metropolitan University, 4 Shinshu
University
We are developing a new resonance scattering lidar system to be installed at Syowa Station (69S, 39E) in Antarctica. For the
new lidar system, we have employed a tunable alexandrite laser covering the resonance scattering lines of two neutral species,
which are atomic potassium (K, 770 nm) and atomic iron (Fe, 386 nm), and two ion species, which are calcium ion (Ca+ , 393nm) and aurorally excited nitrogen ion (N2+ , 390 nm, 391 nm). Thus the new lidar system will provide information on themesosphere and lower thermosphere as well as the ionosphere. Using the new resonance scattering lidar together with colocatedother instruments, we will conduct a comprehensive ground-based observation of the low, middle, and upper atmosphere above
Syowa Station. This unique observation is expected to make important contribution to studies on the atmospheric vertical coupling process and the neutral and charged particle interaction.
In this presentation, we will report current status on test observations of the iron atom layer at National Institute of Polar Research (NIPR) at Tachikawa, Japan (36N, 139E). In order to obtain the iron resonance line at 386 nm, we operate the fundamental
laser (i.e. the tuneable alexandrite laser) at 772 nm, which is shifted by 2 nm from the potassium resonance line at 770 nm, andthen obtain the pulsed 386 nm laser using nonlinear crystal based on the second harmonic generation (SHG) technique. On 14
August 2013, we successfully detected first signals from the iron atom layer, with one-frequency mode for Fe number density
measurement. The observed iron number density would be fairly comparable to that from the previous observations at Illinois(40N, 88W). After that, we have prepared three-frequency mode for Doppler temperature measurements. Based on a theoretical
calculation, we have determined good combination of the three laser frequencies to minimize the temperature error, and thenperformed operations of the three-frequency mode on 5 and 18 Augsut 2014. The obtained temperature data will be comparedwith those from NRLMSISE-00 model and satellite observations. Furthermore, we will show a challenge of observing Ca+
temperature.

Keywords: Resonance scattering lidar, Mesosphere/Lower thermosphere, Ionospheric D/E region, Neutral temperature, Ion temperature

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PEM27-P25

Room:Convention Hall

Time:May 26 18:15-19:30

Report of the STEL optical observation at the Tromsoe EISCAT radar site by March 2015
OYAMA, Shin-ichiro1∗ ; NOZAWA, Satonori1 ; SHIOKAWA, Kazuo1 ; OTSUKA, Yuichi1 ; TSUDA, Takuo2 ;TAKAHASHI, Toru1 ; FUJII, Ryoichi1
1

Solar-Terrestrial Environment Laboratory, 2 Department of Information and Communication Engineering, University of ElectroCommunications
Solar-Terrestrial Environment Laboratory (STEL) has been operating various kinds of optical instruments for more than 10
years at the Tromsφ EISCAT (European Incoherent Scatter) radar site in Norway (69.6o N, 19.2o E), which is one of the stateof-art observatories at high latitudes. Five instruments are now in automatic operation regularly from October to March: (1)three-wavelength photometer (427.8 nm, 630.0 nm, and 557.7 nm), which is fixed to look along the magnetic field line, (2)digital camera for monitoring weather and aurora, (3) proton all-sky camera (486.1 nm), (4) multi-wavelength all-sky camera(557.7 nm, 630.0 nm, OH band, 589.3 nm, 572.5 nm, and 732.0 nm), and (5) Fabry-Perot interferometer (557.7 nm, 630.0
nm, and 732.0 nm). The quick looks are available on the web at www.stelab.nagoya-u.ac.jp/˜eiscat/data/EISCAT.html. These
instruments are programmatically operated, and they have contributed to many campaign observations with the EISCAT radars,
rockets, satellites, and other ground-based instruments by adjusting the observation mode.
Keywords: aurora, air glow, optical instrument, ionosphere, thermosphere, polar region

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PEM27-P26

Room:Convention Hall

Time:May 26 18:15-19:30

Observation of GNSS scintillation in Tromso
UWASHITOMI, Kodai1∗ ; OTSUKA, Yuichi1 ; OGAWA, Yasunobu2 ; HOSOKAWA, Keisuke3
1

Solar-Terrestrial Environment Laboratory, Nagoya University, 2 National Institute of Polar Research, 3 Department of Communication Engineering and Informatics, University of Electro-Communications
Ionospheric scintillation is a phenomenon that received radio wave fluctuates in phase and amplitude. It has been known that
amplitude scintillation frequently occurs at equatorial regions, and that phase scintillation frequently occurs at high latitudes. We
have been operating dual-frequency GNSS (Global Navigation Satellite System) receivers at Tromsoe, Norway. The receivers arecontrolled by PC and record carrier phase and signal-to-noise ratio of the received signal from GPS satellites. We have calculated
S4 and σφ indices. S4 is defined as a ratio of standard deviation of the signal intensity to the average signal intensity in each 1
minute. σφis defined as the standard deviation of the phase of the received signal. During November and December 2013, in 12
days, we observed amplitude scintillation events in which S4 exceeds 0.3.In 7 days out of 5 days, magnetic activity was high. In
this study, we will compare the amplitude scintillation with phase scintillation and total electron content (TEC) obtained fromthe GNSS receivers to discuss generation mechanisms of ionospheric irregularities causing the amplitude scintillations.

Keywords: scintillation, ionosphere, GPS, GNSS, geomagnetic disturbance, TEC

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PEM27-P27

Room:Convention Hall

Time:May 26 18:15-19:30

Statistical analysis of Medium-Scale Traveling Ionospheric Disturbances using a GPS
network at high-latitudes
MIZOGUCHI, Takuya1∗ ; OTSUKA, Yuichi1 ; SHIOKAWA, Kazuo1 ; TSUGAWA, Takuya2 ; NISHIOKA, Michi2
1

Solar-Terrestrial Environment Laboratory, Nagoya University, 2 National Institute of Information and Communications

In our previous study, using global positioning system (GPS) data taken from more than 100 GPS receivers in Alaska in 2012,
we investigated two-dimensional maps of total electron content (TEC) perturbations with a time resolution of 30s and a spatial
resolution of 0.15◦×0.15◦ in longitude and latitude to examine statistical characteristics of Medium-Scale Traveling IonosphericDisturbances (MSTIDs) for the first time. From the statistical analysis of the TEC maps obtained in 2012, we have revealed
some of the characteristics of MSTIDs in Alaska. MSTIDs over Alaska frequently occur in winter from 8 to 20 LT. Maximum
occurrence rate of the MSTIDs in monthly and hourly bins exceeds 50%. Propagation direction of MSTIDs is dominantly
southward or southeastward from 8 to 14 LT and southwestward from 14 to 20 LT.
In this study, we focus on the statistical result of propagation direction. Southward or southeastward propagating MSTIDs is
consistent with that of MSTIDs at mid-latitudes and could be caused by atmospheric gravity waves (AGW) in the thermosphere.
The southwestward propagating MSTIDs have been observed with all-sky airglow imager in Alaska, and are considered to be
attributed to AGW generated by auroral activity. The present study shows that the southwestward propagating MSTIDs appear
before sunset when the airglow observations can be carried out.
In this presentation, we show that statistical characteristics of parameters of MSTIDs, such as period, horizontal wave length,
and propagation velocity, and discuss possibility of TEC perturbation caused by AGW propagation excited by auroral activity.
Also, we investigate propagation direction of MSTIDs more detail using GPS data taken from GPS receiver networks in northern
Europe in 2008 and discuss whether southwestward propagating MSTID is common phenomenon at high-latitudes.
Keywords: Medium-Scale Traveling Ionospheric Disturbances, GPS, auroral activity

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PEM27-P28

Room:Convention Hall

Time:May 26 18:15-19:30

Statistical study of longitude dependencies of MSTIDs observed with GPS networks
YAMAWAKI, Keita1∗ ; OTSUKA, Yuichi1 ; SHIOKAWA, Kazuo1 ; TSUGAWA, Takuya2 ; NISHIOKA, Michi2
1

Solar-Terrestrial Environment Laboratory, Nagoya University, 2 National Institute of Information and Communications Technology
We revealed statistical characteristics of medium-scale traveling ionospheric disturbance (MSTID) by using global positioning
system (GPS) networks in North America and compared them with previous studies.
TEC (Total Electron Content) is obtained from delays of radio wave transmitted GPS satellites to the receivers. Using twodimensional maps of TEC perturbations, for the first time, we statistically analyzed MSTID above North America in 2013. The
observed characteristics can be summarized as follows:
1. The occurrence rate of MSTID above North America during daytime (0800LT-2000LT) is high in winter (November-March)and its propagation direction is predominantly south-eastward. This seasonal variation of daytime MSTID occurrence rate is consistent with that reported by earlier publications. The daytime MSTID could be caused by gravity waves.
2. The occurrence rate of MSTID during nighttime (2200LT-0600LT) is high in summer (May-August) and its propagation
direction is predominantly south-westward. This feature is consistent with that reported in earlier studies. Perkins instability
could play an important role in generating the nighttime MSTID.
3. The occurrence rate of morning MSTID is high throughout the year. Its propagation direction is predominantly eastward
and the gravity waves generated by terminator could account for this type of MSTID.
4. The occurrence rate of MSTID above the west part of North America is 20 percent higher than that above the east part insummer (May-June).The pervious paper shows that occurrence rate of ES layer in west part of North America is higher than thatin east part, on the basis of occultation observations using low orbit satellite. Our statistical result suggests that the coupling
process between E and F regions could play an important role for generating MSTIDs.

Keywords: MSTID, GPS, sporadic E layer, longitude dependencies

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