Faculty Profiles - OTSUKA, Yuichi

Papers - OTSUKA, Yuichi

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Explicit characteristics of evolutionary-type plasma bubbles observed from Equatorial Atmosphere Radar during the low to moderate solar activity years 2010-2012 Reviewed

K. K. Ajith, S. Tulasi Ram, M. Yamamoto, T. Yokoyama, V. Sai Gowtam, Y. Otsuka, T. Tsugawa, K. Niranjan

JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS Vol. 120 ( 2 ) page： 1371 - 1382 2015.2

Language：English Publishing type：Research paper (scientific journal) Publisher：AMER GEOPHYSICAL UNION

Using the fan sector backscatter maps of 47MHz Equatorial Atmosphere Radar (EAR) at Kototabang (0.2 degrees S geographic latitude, 100.3 degrees E geographic longitude, and 10.4 degrees S geomagnetic latitude), Indonesia, the spatial and temporal evolution of equatorial plasma bubbles (EPBs) were examined to classify the evolutionary-type EPBs from those which formed elsewhere and drifted into the field of view of radar. A total of 535 EPBs were observed during the low to moderate solar activity years 2010-2012, out of which about 210 (similar to 39%) are of evolving type and the remaining 325 (similar to 61%) are drifting-in EPBs. In general, both the evolving-type and drifting-in EPBs exhibit predominance during the postsunset hours of equinoxes and December solstices. Interestingly, a large number of EPBs were found to develop even a few minutes prior to the apex sunset during equinoxes. Further, the occurrence of evolving-type EPBs exhibits a clear secondary peak around midnight (2300-0100 LT), primarily, due to higher rate of occurrence during the postmidnight hours of June solstices. A significant number (similar to 33%) of postmidnight EPBs generated during June solstices did not exhibited any clear zonal drift, while about 14% of EPBs drifted westward. Also, the westward drifting EPBs are confined only to June solstices. The responsible mechanisms for the genesis of fresh EPBs during postmidnight hours were discussed in light of equatorward meridional winds in the presence of weak westward electric fields.

DOI： 10.1002/2014JA020878

Web of Science

CDF data archive and integrated data analysis platform for ERG-related ground data developed by ERG Science Center (ERG-SC) Reviewed

Hori, T, Y. Miyashita, Y. Miyoshi, K. Seki, T. Segawa, Y.-M. Tanaka, K. Keika, M. Shoji, I. Shinohara, K. Shiokawa, Y. Otsuka, S. Abe, A. Yoshikawa, K. Yumoto, Y. Obana, N. Nishitani, A. S. Yukimatu, T. Nagatsuma, M. Kunitake, K. Hosokawa, Y. Ogawa, K. T. Murata, M. Nosé, H. Kawano, T. Sakanoi

Journal of Space Science Informatics Japan Vol. JAXA-RR-14-009 page： 75 - 90 2015

GAST-D flight experiment results with disturbed and quiet ionospheric conditions Reviewed

Susumu Saito, Takayuki Yoshihara, Atsushi Kezuka, Shinji Saitoh, Sonosuke Fukushima, Yuichi Otsuka

PROCEEDINGS OF THE 28TH INTERNATIONAL TECHNICAL MEETING OF THE SATELLITE DIVISION OF THE INSTITUTE OF NAVIGATION (ION GNSS+ 2015) page： 1494 - 1499 2015

Language：English Publishing type：Research paper (international conference proceedings) Publisher：INST NAVIGATION

GAST-D ground prototype and and GAST-D airborne experimental subsystem have been developed. The GAST-D ground prototype was installed at New Ishigaki Airport located in the low magnetic latitude region. With the ground prototype and the airborne experimental system, GAST-D flight experiments in the low magnetic latitude region under ionospheric quiet and disturbed conditions for the first time in the world.
Two flight campaigns were conducted in March and September 2014. In the campaign carried out in September 2014, the vertical error performances were comparable between ionospheric quiet and disturbed condition. However, availability degradation during the severely disturbed condition is an issue. The DSIGMA monitor which is one of the airborne integrity monitors was confirmed by all-sky airglow measurements to react ionospheric disturbance.
The next steps of the study include parameter tuning of the ground prototype and airborne experimental system to enhance service availability during ionospheric disturbed conditions.

Web of Science

Direct observations of blob deformation during a substorm Reviewed

T. Ishida, Y. Ogawa, A. Kadokura, K. Hosokawa, Y. Otsuka

ANNALES GEOPHYSICAE Vol. 33 ( 5 ) page： 525 - 530 2015

Language：English Publishing type：Research paper (scientific journal) Publisher：COPERNICUS GESELLSCHAFT MBH

Ionospheric blobs are localized plasma density enhancements, which are mainly produced by the transportation process of plasma. To understand the deformation process of a blob, observations of plasma parameters with good spatial-temporal resolution are desirable. Thus, we conducted the European Incoherent Scatter radar observations with high-speed meridional scans (60-80 s) during October and December 2013, and observed the temporal evolution of a blob during a substorm on 4 December 2013. This paper is the first report of direct observations of blob deformation during a substorm. The blob deformation arose from an enhanced plasma flow shear during the substorm expansion phase, and then the blob split into two smaller-scale blobs, whose scale sizes were more than similar to 100 km in latitude. Our analysis indicates that the Kelvin-Helmholtz instability and dissociative recombination could have deformed the blob structure.

DOI： 10.5194/angeocom-33-525-2015

Web of Science

Climatology of Equatorial Plasma Bubble Observed by MyRTKnet over the Years 2008-2013 Reviewed

S. M. Buhari, M. Abdullah, T. Yokoyama, A. M. Hasbi, Y. Otsuka, M. Nishioka, S. A. Bahari, T. Tsugawa

2015 INTERNATIONAL CONFERENCE ON SPACE SCIENCE AND COMMUNICATION (ICONSPACE) page： 101 - 105 2015

Language：English Publishing type：Research paper (international conference proceedings) Publisher：IEEE

Malaysia Real-Time Kinematics GNSS Network (MyRTKnet) which consists of 78 GPS receivers was used to investigate the occurrence of equatorial plasma bubble (EPB) along 96 degrees E - 120 degrees E longitude. In this study, we present the monthly occurrence rate of EPB along the geographical longitudes of 96 degrees E - 120 degrees E for a half of solar cycle period (2008 - 2013). A 2D map of rate of TEC change index (ROTI) projected at 300 km altitude was derived from the signal paths between GPS satellites and the receivers. A ROTI keogram for one day period was obtained from the east-west cross section of the 2D ROTI maps at 4 degrees N for every 5 min. The occurrence day of EPB was determined from the keogram by the existence of ROTI larger than 0.1 TECU/min within the 96 degrees E - 120 degrees E longitude. The results show that the occurrence of EPB along the 96 degrees E - 120 degrees E has maximum during equinoctial months and is consistent with previous studies. The occurrence rate of EPB during equinoctial months shows similar characteristics in low and high solar activity due to the broad observational coverage of the MyRTKnet. In contrast, the occurrence rate of EPB during solstice months shows significant relation with solar activity. Solstice months recorded high occurrence rate of EPB in high solar activity that might be attributed to post-midnight irregularities.

DOI： 10.1109/IconSpace.2015.7283752

Web of Science

Long-term variation in the upper atmosphere as seen in the geomagnetic solar quiet daily variation Reviewed

Atsuki Shinbori, Yukinobu Koyama, Masahito Nose, Tomoaki Hori, Yuichi Otsuka, Akiyo Yatagai

EARTH PLANETS AND SPACE Vol. 66 2014.12

Language：English Publishing type：Research paper (scientific journal) Publisher：SPRINGER HEIDELBERG

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

DOI： 10.1186/s40623-014-0155-1

Web of Science

CME front and severe space weather Reviewed

N. Balan, R. Skoug, S. Tulasi Ram, P. K. Rajesh, K. Shiokawa, Y. Otsuka, I. S. Batista, Y. Ebihara, T. Nakamura

JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS Vol. 119 ( 12 ) 2014.12

Language：English Publishing type：Research paper (scientific journal) Publisher：AMER GEOPHYSICAL UNION

Thanks to the work of a number of scientists who made it known that severe space weather can cause extensive social and economic disruptions in the modern high-technology society. It is therefore important to understand what determines the severity of space weather and whether it can be predicted. We present results obtained from the analysis of coronal mass ejections (CMEs), solar energetic particle (SEP) events, interplanetary magnetic field (IMF), CME-magnetosphere coupling, and geomagnetic storms associated with the major space weather events since 1998 by combining data from the ACE and GOES satellites with geomagnetic parameters and the Carrington event of 1859, the Quebec event of 1989, and an event in 1958. The results seem to indicate that (1) it is the impulsive energy mainly due to the impulsive velocity and orientation of IMF B-z at the leading edge of the CMEs (or CME front) that determine the severity of space weather. (2) CMEs having high impulsive velocity (sudden nonfluctuating increase by over 275 km s(-1) over the background) caused severe space weather (SvSW) in the heliosphere (failure of the solar wind ion mode of Solar Wind Electron Proton Alpha Monitor in ACE) probably by suddenly accelerating the high-energy particles in the SEPs ahead directly or through the shocks. (3) The impact of such CMEs which also show the IMF B-z southward from the leading edge caused SvSW at the Earth including extreme geomagnetic storms of mean Dst(MP) < -250 nT during main phases, and the known electric power outages happened during some of these SvSW events. (4) The higher the impulsive velocity, the more severe the space weather, like faster weather fronts and tsunami fronts causing more severe damage through impulsive action. (5) The CMEs having IMF B-z northward at the leading edge do not seem to cause SvSW on Earth, although, later when the IMF B-z turns southward, they can lead to super geomagnetic storms of intensity (Dst(min)) less than even -400 nT.

DOI： 10.1002/2014JA020151

Web of Science

Continuous generation and two-dimensional structure of equatorial plasma bubbles observed by high-density GPS receivers in Southeast Asia Reviewed

S. M. Buhari, M. Abdullah, A. M. Hasbi, Y. Otsuka, T. Yokoyama, M. Nishioka, T. Tsugawa

JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS Vol. 119 ( 12 ) 2014.12

Language：English Publishing type：Research paper (scientific journal) Publisher：AMER GEOPHYSICAL UNION

High-density GPS receivers located in Southeast Asia (SEA) were utilized to study the two-dimensional structure of ionospheric plasma irregularities in the equatorial region. The longitudinal and latitudinal variations of tens of kilometer-scale irregularities associated with equatorial plasma bubbles (EPBs) were investigated using two-dimensional maps of the rate of total electron content change index (ROTI) from 127 GPS receivers with an average spacing of about 50-100 km. The longitudinal variations of the two-dimensional maps of GPS ROTI measurement on 5 April 2011 revealed that 16 striations of EPBs were generated continuously around the passage of the solar terminator. The separation distance between the subsequent onset locations varied from 100 to 550 km with 10 min intervals. The lifetimes of the EPBs observed by GPS ROTI measurement were between 50 min and over 7 h. The EPBs propagated 440-3000 km toward the east with velocities of 83-162 m s(-1). The longitudinal variations of EPBs by GPS ROTI keogram coincided with the depletions of 630 nm emission observed using the airglow imager. Six EPBs were observed by GPS ROTI along the meridian of Equatorial Atmosphere Radar (EAR), while only three EPBs were detected by the EAR. The high-density GPS receivers in SEA have an advantage of providing time continuous descriptions of latitudinal/longitudinal variations of EPBs with both high spatial resolution and broad geographical coverage. The spatial periodicity of the EPBs could be associated with a wavelength of the quasiperiodic structures on the bottomside of the F region which initiate the Rayleigh-Taylor instability.

DOI： 10.1002/2014JA020433

Web of Science

Airglow observations of nighttime medium-scale traveling ionospheric disturbances from Yonaguni: Statistical characteristics and low-latitude limit Reviewed

V. Lakshmi Narayanan, K. Shiokawa, Y. Otsuka, S. Saito

JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS Vol. 119 ( 11 ) page： 9268 - 9282 2014.11

Language：English Publishing type：Research paper (scientific journal) Publisher：AMER GEOPHYSICAL UNION

The characteristics of nighttime medium-scale traveling ionospheric disturbance (MSTID) features observed over Yonaguni (24.5 degrees N, 123.0 degrees E; 19.3 degrees N dip latitude), Japan are studied using all-sky imaging of OI 630.0nm airglow emission. The uniqueness of these observations is that the area observed by the imager covers the transition region between low to middle latitudes in the ionosphere. Typical low-latitude limit of midlatitude-type nighttime MSTIDs possessing phase front alignments along the northwest to the southeast occurs in this region. These MSTID features are rarely sighted at dip latitudes below 15 degrees. We selected 2 year period for analysis in which 1 year corresponded to the solar minimum conditions and another year to the solar maximum conditions. The MSTIDs were observed to extend to farther lower latitudes during the solar minimum conditions than during the solar maximum periods. Their observed range of wavelengths, phase velocities, phase front alignment, and propagation directions are similar to those observed at typical midlatitude sites. However, on many occasions the phase fronts of the observed MSTIDs did not extend over the whole field of view of the imager indicating that some process inhibits their extension to further lower latitudes. Detailed investigation suggests that the poleward propagating enhancement of airglow intensity, probably associated with the midnight pressure bulge, causes the MSTID features to disappear when they reach lower latitudes later in the night. When the MSTIDs reach lower latitudes well before midnight, they are found to be inhibited by the equatorial ionization anomaly crest region.

DOI： 10.1002/2014JA020368

Web of Science

First spaceborne observation of the entire concentric airglow structure caused by tropospheric disturbance Reviewed

Y. Akiya, A. Saito, T. Sakanoi, Y. Hozumi, A. Yamazaki, Y. Otsuka, M. Nishioka, T. Tsugawa

GEOPHYSICAL RESEARCH LETTERS Vol. 41 ( 19 ) page： 6943 - 6948 2014.10

Language：English Publishing type：Research paper (scientific journal) Publisher：AMER GEOPHYSICAL UNION

Spaceborne imagers are able to observe the airglow structures with wide field of views regardless of the tropospheric condition that limits the observational time of the ground-based imagers. Concentric wave structures of the O-2 airglow in 762 nm wavelength were observed over North America on 1 June 2013 from the International Space Station. This was the first observation in which the entire image of the structure was captured from space, and its spatial scale size was determined to be 1200 km radius without assumptions. The apparent horizontal wavelength was 80 km, and the amplitude in the intensity was approximately 20% of the background intensity. The propagation velocity of the structure was derived as 125 +/- 62 m/s and atmospheric gravity waves were estimated to be generated for 3. 5 +/- 1. 7 h. Concentric structures observed in this event were interpreted to be generated by super cells that caused a tornado in its early phase.

DOI： 10.1002/2014GL061403

Web of Science

Auroral fragmentation into patches Reviewed

Kazuo Shiokawa, Ayumi Hashimoto, Tomoaki Hori, Kaori Sakaguchi, Yasunobu Ogawa, Eric Donovan, Emma Spanswick, Martin Connors, Yuichi Otsuka, Shin-Ichiro Oyama, Satonori Nozawa, Kathryn McWilliams

JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS Vol. 119 ( 10 ) page： 8249 - 8261 2014.10

Language：English Publishing type：Research paper (scientific journal) Publisher：AMER GEOPHYSICAL UNION

Auroral patches in diffuse auroras are very common features in the postmidnight local time. However, the processes that produce auroral patches are not yet well understood. In this paper we present two examples of auroral fragmentation which is the process by which uniform aurora is broken into several fragments to form auroral patches. These examples were observed at Athabasca, Canada (geomagnetic latitude: 61.7 degrees N), and TromsO, Norway (67.1 degrees N). Captured in sequences of images, the auroral fragmentation occurs as finger-like structures developing latitudinally with horizontal-scale sizes of 40-100 km at ionospheric altitudes. The structures tend to develop in a north-south direction with speeds of 150-420 m/s without any shearing motion, suggesting that pressure-driven instability in the balance between the earthward magnetic-tension force and the tailward pressure gradient force in the magnetosphere is the main driving force of the auroral fragmentation. Therefore, these observations indicate that auroral fragmentation associated with pressure-driven instability is a process that creates auroral patches. The observed slow eastward drift of aurora during the auroral fragmentation suggests that fragmentation occurs in low-energy ambient plasma.

DOI： 10.1002/2014JA020050

Web of Science

Diagnostics of equatorial and low latitude ionosphere by TEC mapping over Brazil Reviewed

H. Takahashi, S. Costa, Y. Otsuka, K. Shiokawa, J. F. G. Monico, E. Paula, P. Nogueira, C. M. Denardini, F. Becker-Guedes, C. M. Wrasse, A. S. Ivo, V. C. F. Gomes, W. Gargarela, N. Sant'Anna, R. Gatto

ADVANCES IN SPACE RESEARCH Vol. 54 ( 3 ) page： 385 - 394 2014.8

Language：English Publishing type：Research paper (scientific journal) Publisher：ELSEVIER SCI LTD

The total electron content (TEC) in the equatorial and low-latitude ionosphere over Brazil was monitored in two dimensions by using 2011 data from the ground-based global navigation satellite system (GNSS) receiver network operated by the Brazilian Institute for Geography and Statistics. It was possible to monitor the spatial and temporal variations in TEC over Brazil continuously during both day and night with a temporal interval of 10 mm and a spatial resolution of about 400 km. The daytime equatorial ionization anomaly (ETA) and post-sunset plasma enhancement (PS-ETA) were monitored over an area corresponding to a longitudinal extension of 4000 km in South America. Considerable day-to-day variation was observed in ETA and PS-ETA. A large latitudinal and longitudinal gradient of TEC indicated a significant ionospheric range error in application of the GNSS positioning system. Large-scale plasma bubbles after sunset were also mapped over a wide range. Depletions with longitudinally separated by more than 800 km were observed. They were extended by more than 2000 km along the magnetic field lines and drifted eastward. It is expected that 2-dimensional TEC mapping can serve as a useful tool for diagnosing ionospheric weather, such as temporal and spatial variation in the equatorial plasma trough and crest, and particularly for monitoring the dynamics of plasma bubbles. (C) 2014 COSPAR. Published by Elsevier Ltd. All rights reserved.

DOI： 10.1016/j.asr.2014.01.032

Web of Science

Observations of GPS scintillation during an isolated auroral substorm Reviewed

Hosokawa, K, Y. Otsuka, Y. Ogawa, T. Tsugawa

Progress in Earth and Planetary Sciencs Vol. 96693290710.1186/2197-4284-1-1 2014.8

Vertical ExB drifts from radar and C/NOFS observations in the Indian and Indonesian sectors: Consistency of observations and model Reviewed

A. K. Patra, P. Pavan Chaitanya, Y. Otsuka, T. Yokoyama, M. Yamamoto, R. A. Stoneback, R. A. Heelis

JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS Vol. 119 ( 5 ) page： 3777 - 3788 2014.5

Language：English Publishing type：Research paper (scientific journal) Publisher：AMER GEOPHYSICAL UNION

In this paper, we analyze vertical ExB drifts obtained from the Doppler shifts of the daytime 150km radar echoes from two radar stations located off the magnetic equator, namely, Gadanki in India and Kototabang in Indonesia, and compare those with corresponding Coupled Ion Neutral Dynamics Investigation (CINDI) observations onboard the C/NOFS satellite and the Scherliess-Fejer model in an effort to understand to what extent the low-latitude vertical ExB drifts of the 150km region represent the F region vertical ExB drifts. The radar observations were made during 9-16 LT in January, June, July, and December 2009. A detailed comparison reveals that vertical ExB drifts observed by the radars at both locations agree well with those of CINDI and differ remarkably from those of the model. Importantly, the model and observed drifts show large disagreement when the observed drifts are either large or downward. Further, while the CINDI as well as the radar observations from the two longitudes are found to agree with each other on the average, they differ remarkably on several occasions when compared on a one-to-one basis. The observed difference in detail is due to measurements made in different volumes linked with latitudinal and/or longitudinal differences and underlines the role of neutral dynamics linked with tides and gravity waves in the two longitude sectors on the respective vertical ExB drifts. The results presented here are the first of their kind and are expected to have wider applications in furthering our understanding on fine-scale longitudinal variabilities in the ionosphere in general and ionospheric electrodynamics in the Indian and Indonesian sectors in particular.

DOI： 10.1002/2013JA019732

Web of Science

Global imaging of polar cap patches with dual airglow imagers Reviewed

K. Hosokawa, S. Taguchi, K. Shiokawa, Y. Otsuka, Y. Ogawa, M. Nicolls

GEOPHYSICAL RESEARCH LETTERS Vol. 41 ( 1 ) page： 1 - 6 2014.1

Language：English Publisher：AMER GEOPHYSICAL UNION

During a 2 h interval from 2240 to 2440 UT on 12 November 2012, regions of increased 630.0 nm airglow emissions were simultaneously detected by dual all-sky imagers in the polar cap, one at Longyearbyen, Norway (78.1 degrees N, 15.5 degrees E) and the other at Resolute Bay, Canada (74.7 degrees N, 265.1 degrees E). The Resolute Bay incoherent scatter radar observed clear enhancements of the F region electron density up to 10(12) m(-3) within these airglow structures which indicates that these are optical manifestations of polar cap patches propagating across the polar cap. During this interval of simultaneous airglow imaging, the nightside/dawnside (dayside/duskside) half of the patches was captured by the imager at Longyearbyen (Resolute Bay). This unique situation enabled us to estimate the dawn-dusk extent of the patches to be around 1500 km, which was at least 60-70% of the width of the antisunward plasma stream seen in the Super Dual Auroral Radar Network convection maps. In contrast to the large extent in the dawn-dusk direction, the noon-midnight thickness of each patch was less than 500 km. These observations demonstrate that there exists a class of patches showing cigar-shaped structures. Such patches could be produced in a wide range of local time on the dayside nearly simultaneously and spread across many hours of local time soon after their generation.

DOI： 10.1002/2013GL058748

Web of Science

Drift Velocities of 150-km Field-Aligned Irregularities Observed by the Equatorial Atmosphere Radar Reviewed

Otsuka Y., Mizutani, N., Shiokawa, K., Patra, A., Yokoyama, T., and Yamamoto

Antarctic Record page：印刷中 2014

The observation of equatorial plasma bubble using all sky imager and GPS TEC measurement Reviewed

Suhaila M. Buhari, Mardina Abdullah, Alina Marie Hasbi, Yuichi Otsuka, Siti Aminah Bahari, Mohd Hezri Mokhtar, Michi Nishioka, Takuya Tsugawa

2014 XXXITH URSI GENERAL ASSEMBLY AND SCIENTIFIC SYMPOSIUM (URSI GASS) 2014

Language：English Publishing type：Research paper (international conference proceedings) Publisher：IEEE

In this study, the two-dimensional horizontal structure of EPB was observed using GPS total electron content (TEC) measurement in South East Asia region. Rate of TEC index (ROTI) is calculated from GPS TEC measurement and plotted onto two-dimensional map in geographic coordinate. Depletion of The OI 630.0 nm emission is completely coincided with ROTI enhancement region from GPS TEC measurement. Therefore, the observation using GPS TEC measurement is able to provide spatial and temporal properties of EPB in SEA region.

Web of Science

国際宇宙ステーションからの超高層大気撮像観測ミッションISS-IMAPの現状

齊藤昭則, 秋谷祐亮, 穂積裕太, 山崎敦, 阿部琢美, 鈴木睦, 村上豪, 坂野井健, 吉川一朗, 大塚雄一, 藤原均, 田口真, 山本衛, 中村卓司, 江尻省, 菊池雅行, 河野英昭, Huixin Liu, 石井守, 久保田実, 津川卓也, 星野尾一明, 坂野井和代, IMAPワーキンググループ

第14回宇宙科学シンポジウム講演集 2014

国際宇宙ステーションからの大気光観測による赤道域電離圏擾乱の研究

山田貴宣, 大塚雄一, 坂野井健, 山崎敦, 齊藤昭則, 秋谷祐亮

第28回大気圏シンポジウム講演集 2014

Vertical ExB drifts from radar and C/NOFS observations in the Indian and Indonesian sectors: Consistency of observations and model Reviewed

A. K. Patra, P. Pavan Chaitanya, Y. Otsuka, T. Yokoyama, M. Yamamoto, R. A. Stoneback, R. A. Heelis

Journal of Geophysical Research: Space Physics Vol. 119 ( 5 ) page： 3777 - 3788 2014

Language：English Publishing type：Research paper (scientific journal) Publisher：Blackwell Publishing Ltd

In this paper, we analyze vertical ExB drifts obtained from the Doppler shifts of the daytime 150 km radar echoes from two radar stations located off the magnetic equator, namely, Gadanki in India and Kototabang in Indonesia, and compare those with corresponding Coupled Ion Neutral Dynamics Investigation (CINDI) observations onboard the C/NOFS satellite and the Scherliess-Fejer model in an effort to understand to what extent the low-latitude vertical ExB drifts of the 150 km region represent the F region vertical ExB drifts. The radar observations were made during 9-16 LT in January, June, July, and December 2009. A detailed comparison reveals that vertical ExB drifts observed by the radars at both locations agree well with those of CINDI and differ remarkably from those of the model. Importantly, the model and observed drifts show large disagreement when the observed drifts are either large or downward. Further, while the CINDI as well as the radar observations from the two longitudes are found to agree with each other on the average, they differ remarkably on several occasions when compared on a one-to-one basis. The observed difference in detail is due to measurements made in different volumes linked with latitudinal and/or longitudinal differences and underlines the role of neutral dynamics linked with tides and gravity waves in the two longitude sectors on the respective vertical ExB drifts. The results presented here are the first of their kind and are expected to have wider applications in furthering our understanding on fine-scale longitudinal variabilities in the ionosphere in general and ionospheric electrodynamics in the Indian and Indonesian sectors in particular. Key Points First comparison of 150 km echo and C/NOFS ExB drifts over India and Indonesia These observations agree at both locations and show some longitudinal difference Radar and C/NOFS observations differ remarkably from model ©2014. American Geophysical Union. All Rights Reserved.

DOI： 10.1002/2013JA019732

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Papers - OTSUKA, Yuichi