Faculty Profiles - SHINBORI Atsuki

Storm-time electron density enhancement in the cleft ion fountain Reviewed Open Access

N. Kitamura, Y. Nishimura, M. O. Chandler, T. E. Moore, N. Terada, T. Ono, A. Shinbori, A. Kumamoto

JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS Vol. 117 ( 11 ) 2012.11

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

To determine the characteristics and origin of observed storm-time electron density enhancements in the polar cap, and to investigate the spatial extent (noon-midnight direction) of associated O+ ion outflows, we analyzed nearly simultaneous observations of such electron density enhancements from the Akebono satellite and ion upflows from the Polar satellite during a geomagnetic storm occurring on 6 April 2000. The Akebono satellite observed substantial electron density enhancements by a factor of similar to 10-90 with a long duration of similar to 15 h at similar to 2 R-E in the southern polar region. The Polar satellite outflow measurements in the northern polar cap at similar to 7-4 R-E exhibited velocity filtering of the similar to 100 eV to similar to 0 eV (from the spacecraft potential) ion outflow from the cleft ion fountain, with resultant temperatures declining from similar to 3 eV to 0.03 eV with increasing distance from the cusp. Similar velocity filtering was detected in the southern polar cap at similar to 1.8-3.5 RE. The region of O+ ion outflows with fluxes exceeding 5 x 10(8) /cm(2)/s (mapped to 1000 km altitude) extended similar to 10 degrees MLAT (similar to 1000 km) at the ionosphere from the cusp/cleft into the dayside polar cap at similar to 2.5 RE. These coordinated Akebono-Polar observations are consistent with the development of storm-time electron density enhancements in the polar cap as a result of the bulk outflow of low-energy plasma as part of the cleft ion fountain. The large spatial scale, large ion fluxes, and the long duration indicate significant supply of very-low-energy O+ ions to the magnetosphere through this region.

DOI： 10.1029/2012JA017900

Magnetic local time and latitude dependence of amplitude of the main impulse (MI) of geomagnetic sudden commencements and its seasonal variation Reviewed

Atsuki Shinbori, Yuji Tsuji, Takashi Kikuchi, Tohru Araki, Akihiro Ikeda, Teiji Uozumi, Dmitry Baishev, Boris M. Shevtsov, Tsutomu Nagatsuma, Kiyohumi Yumoto

JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS Vol. 117 ( 8 ) 2012.8

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

The magnetic local time and latitude dependence of amplitude of the main impulse (MI) of geomagnetic sudden commencements (SCs) and its seasonal variation have been investigated using high time resolution (1-3 sec) geomagnetic data in the latitudinal range 27-70 degrees for the period 1996-2010. The daytime distribution of the SC-MI amplitude in the sub-auroral and middle latitudes (35-60 degrees) is similar to the DP-2 type geomagnetic variation which shows negative and positive changes in the morning and afternoon, respectively. The magnetic field variation is reversed around the magnetic latitude of 63-65 degrees. This suggests that a pair of field-aligned currents (FACs), resembling the region-1 (R-1) FACs, is located near the magnetic latitude of 63-65 degrees. The nighttime SC amplitude is enhanced significantly in the low and middle latitudes (27-60 degrees). The enhancement is due to the magnetic effect produced by the SC-MI FACs. In the nighttime auroral latitude (63-65 degrees), the SC amplitude decreases steeply due to the enhanced westward auroral electrojet associated with the compression of the magnetosphere. The size of the diurnal variation tends to increase significantly during the summer, compared with that during the winter. This seasonal variation suggests that the DP-2 type ionospheric currents (ICs) and FACs generated during the SC-MI phase are intensified by increased ionospheric conductivities during the summer. It can be concluded that the large-scale MI current system in the ionosphere and magnetosphere is voltage generator.

DOI： 10.1029/2012JA018006

Magnetic latitude and local time distributions of ionospheric currents during a geomagnetic storm Reviewed Open Access

Yuji Tsuji, Atsuki Shinbori, Takashi Kikuchi, Tsutomu Nagatsuma

JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS Vol. 117 ( 7 ) 2012.7

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

In order to clarify the global distribution of ionospheric currents during a geomagnetic storm, we analyzed ground magnetic disturbances from high latitudes to the magnetic equator for the storm on September 7-8, 2002, with the minimum SYM-H value of -168 nT. In this analysis, we investigated magnetic field deviations in the northward component from the SYM-H, as functions of the dipole magnetic latitude (DMLAT) and the magnetic local time (MLT). During the main phase of the storm, the deviations at the low latitudes (10 degrees-35 degrees in DMLAT) were positive/negative in the dawn/dusk (0-9/11-24 h MLT) sector. On the other hand, the deviations at the dayside middle latitudes (35 degrees-55 degrees in DMLAT) were negative/positive in the morning/afternoon (6-12/13-15 h MLT) sector. The local time distribution at the low latitudes may represent the dawn-dusk asymmetry of the storm time ring current, while that at the dayside middle latitudes coincides with the DP2 currents due to the convection electric field associated with the Region 1 field-aligned currents (R1 FACs). All over the nightside middle latitude, the deviations were positive. This implies the direct effect of the R1 FACs through the Biot-Savart's law. At the geomagnetic equator, the eastward and westward electrojets were intensified on the day and nightside, respectively, being caused by the penetrated dawn-to-dusk convection electric field. We found that the MLT distribution of the magnetic deviations during the recovery phase was in opposite sense to that during the main phase at the dayside middle latitudes. The reversed magnetic disturbances must be due to the overshielding electric field associated with the Region 2 field-aligned currents (R2 FACs). Similarly, the deviations at the dayside and nightside equator were reversed, indicating penetration of the dusk-to-dawn overshielding electric field into the equatorial ionosphere. Based on the above results, we propose a current system including the ionospheric currents at middle latitudes caused by the R1/R2 FACs, equatorial EEJ/CEJ, and asymmetric ring current, during the main/recovery phase of the geomagnetic storm.

DOI： 10.1029/2012JA017566

Design of IUGONET metadata format and development of metadata management system (Journal of Space Science Informatics Japan No.1) Reviewed

Development of IUGONET data analysis software Reviewed

田中良昌, 新堀淳樹, 鍵谷将人, 堀智昭, 阿部修司, 小山幸伸, 林寛生, 吉田大紀, 河野貴久, 上野悟, 金田直樹, 米田瑞生, 田所裕康, 元場哲郎, 三好由純, 関華奈子, 宮下幸長, 瀬川朋紀, 小川泰信

宇宙航空研究開発機構研究開発報告 JAXA-RR- Vol. 1巻 ( 11-007 ) page： 91 - 98 2012.3

ＩＵＧＯＮＥＴ共通メタデータフォーマットの策定とメタデータ登録管理システムの開発 Reviewed

堀智昭, 鍵谷将人, 田中良昌, 林寛生, 上野悟, 吉田大紀, 阿部修司, 小山幸伸, 河野貴久, 金田直樹, 新堀淳樹, 田所裕康, 米田瑞生

宇宙航空研究開発機構研究開発報告 JAXA-RR- ( 11-007 ) page： 105 - 111 2012.3

超高層物理学分野の為のメタデータ・データベースの開発 Reviewed

小山幸伸, 河野貴久, 堀智昭, 阿部修, 吉田大紀, 林寛生, 田中良昌, 新堀淳樹, 上野悟, 金田直樹, 米田瑞生, 元場哲郎, 鍵谷将人, 田所裕康

宇宙航空研究開発機構研究開発報告 JAXA-RR- ( 11-007 ) page： 99 - 104 2012.3

大学間連携プロジェクト「超高層大気長期変動の全球地上ネットワーク観測・研究」 Reviewed

林寛生, 小山幸伸, 堀智昭, 田中良昌, 新堀淳樹, 鍵谷将人, 阿部修司, 河野貴久, 吉田大紀, 上野悟, 金田直樹, 米田瑞生, 田所裕康, 元場哲郎

宇宙航空研究開発機構研究開発報告 JAXA-RR- ( 11-007 ) page： 113 - 120 2012.3

Metadata Database Development for Upper Atmosphere Reviewed

KOYAMA Yukinobu, KOUNO Takahisa, HORI Tomoaki, ABE Shuji, YOSHIDA Daiki, HAYASHI Hiroo, TANAKA Yoshimasa, SHINBORI Atsuki, UENO Satoru, KANEDA Naoki, YONEDA Mizuki, MOTOBA Tetsuro, KAGITANI Masato, TADOKORO Hiroyasu

JAXA research and development report Vol. 11 page： 99 - 104 2012.3

Language：Japanese Publishing type：Research paper (scientific journal) Publisher：Japan Aerospace Exploration Agency

We have been building the metadata database of the gound-based observational data for upper atmosphere as developers of the Inter-university Uppear atmosphere Global Observation NETwork (IUGONET) project which is a six year research project from fiscal 2009 by the five Japanese universities and institutes. The main purpose of the metadata database to facilitate access is the improvement of accessibility to the various kinds of the observational data which are distributed to many databases in the various institutes. We designed the IUGONET common metadata format which is based on the SPASE data model/metadata format developed by the SPASE Consortium. Then we customized DSpace, a free repository software, which handles the Dublin Core metadata format by default, to handle the IUGONET common metadata. In this paper, we describe the IUGONET metadata database as a case example of metadata database adaptation for geoscience.

HORI Tomoaki, KAGITANI Masato, TANAKA Yoshimasa, HAYASHI Hiroo, UeNo Satoru, YOSHIDA Daiki, ABE Shuji, KOYAMA Yukinobu, KOUNO Takahisa, KANEDA Naoki, SHINBORI Atsuki, TADOKORO Hiroyasu, YONEDA Mizuki

JAXA research and development report Vol. 11 page： 105 - 111 2012.3

Language：Japanese Publishing type：Research paper (scientific journal) Publisher：Japan Aerospace Exploration Agency

This paper reports on the common metadata format and the metadata management system developed by the Inter-university Upper atmosphere Global Observation NETwork (IUGONET) project. The IUGONET common metadata format has been designed on the basis of the Space Physics Archive Search and Extract (SPASE) data model/metadata format, which has been developed by the SPASE consortium, with some modifications made by IUGONET to accommodate metadata for the various kinds of ground observational data produced by the IUGONET institutes and universities. We have also developed the registration/management system for metadata XML files using GIT, which is a widely-used version control software. With the designed metadata format and the metadata management system, IUGONET continues to generate and archive metadata for the observational data of Japanese Solar-Terrestrial physics community.

CiNii Research

Development of IUGONET data analysis software (Journal of Space Science Informatics Japan No.1) Reviewed

TANAKA Yoshimasa, SHINBORI Atsuki, KAGITANI Masato, HORI Tomoaki, ABE Shuji, KOYAMA Yukinobu, HAYASHI Hiroo, YOSHIDA Daiki, KONO Takahisa, UeNo Satoru, KANEDA Naoki, YONEDA Mizuki, TADOKORO Hiroyasu, MOTOBA Tetsuo, MIYOSHI Yoshizumi, SEKI Kanako, MIYASHITA Yukinaga, SEGAWA Tomonori, OGAWA Yasunobu

JAXA research and development report Vol. 11 page： 91 - 98 2012.3

Language：Japanese Publishing type：Research paper (scientific journal) Publisher：Japan Aerospace Exploration Agency

In this paper we report an outline of data analysis software developed by the IUGONET (Inter-university Upper atmosphere Global Observation NETwork) project. UDAS (iUgonet Data Analysis Software) is the software to visualize and analyze the upper atmospheric data distributed by five universities/institutes (Tohoku Univ., Nagoya Univ., Kyoto Univ., Kyushu Univ., and NIPR) that belong to the IUGONET project. The UDAS is a plug-in software of TDAS (THEMIS Data Analysis Software suite) that is written in IDL (Interactive Data Language) and has many useful routines to visualize and analyze time series data. In addition, the UDAS provides the GUI (Graphical User Interface) for beginners of IDL. A beta version of the UDAS was released at the IUGONET website in May, 2011. Furthermore, future perspectives of the UDAS are described.

CiNii Research

Inter-university Upper atmosphere Global Observation NETwork (IUGONET) project (Journal of Space Science Informatics Japan No.1) Reviewed

HAYASHI Hiroo, KOYAMA Yukinobu, HORI Tomoaki, TANAKA Yoshimasa, SHINBORI Atsuki, KAGITANI Masato, ABE Shuji, KOUNO Takahisa, YOSHIDA Daiki, UeNo Satoru, KANEDA Naoki, YONEDA Mizuki, TADOKORO Hiroyasu, MOTOBA Tetsuo

JAXA research and development report Vol. 11 page： 113 - 120 2012.3

Language：Japanese Publishing type：Research paper (scientific journal) Publisher：Japan Aerospace Exploration Agency

This paper describes an overview of the Inter-university Upper atmosphere Global Observation NETwork (IUGONET) project and briefly mentions important products to be developed in the project. It is an inter-university program by the National Institute of Polar Research, Tohoku University, Nagoya University, Kyoto University, and Kyushu University to build a database of metadata for ground-based observations of the upper atmosphere. The metadata database will be of great help to researchers in efficiently finding and obtaining observational data spread over the universities and institutes. This should also facilitate synthetic analysis of multi-disciplinary data, which will lead to new types of research in the upper atmosphere. The IUGONET development team designs its metadata format based on the SPASE (Space Physics Archive Search and Extract) data model. Some modifications depending on characteristics of ground-based observations of the upper atmosphere are added. The metadata database system is built on the platform of DSpace with customizations according to the IUGONET metadata. In addition, an analysis software for the observational data provided by the IUGONET institutions is developed based on the TDAS (THEMIS Data Analysis Software suite) library written in IDL (Interactive Data Language).

CiNii Research

Effect of R2-FAC development on the ionospheric electric field pattern deduced by a global ionospheric potential solver Reviewed Open Access

Nakamizo, A. Y. Hiraki, Y. Ebihara, T. Kikuchi, K. Seki, T. Hori, A. Ieda, Y. Miyoshi, Y. Tsuji, Y. Nishimura, A. Shinbori

Journal of Geophysical Research, Volume 117, Issue A9, CiteID: A09231, doi: 10.1029/2012JA017669 Vol. 117 ( 9 ) 2012

Language：English Publishing type：Research paper (scientific journal)

Toward the understanding of the effect of the magnetosphere originated disturbances on the global ionospheric electric field and current system, we developed a two-dimensional ionospheric potential solver based on the so-called "thin shell model." The important extension from the previous studies is that our model covers the pole-to-pole ionosphere without placing any boundary at the equator. By using this solver, we investigate how the ionospheric electric field changes from undershielding condition to overshielding condition as the field aligned current (FAC) distribution changes. Calculations are performed by changing IR2/IR1 (the ratio of current intensities of region 2 (R2) and region 1 (R1) FACs) and by moving R2-FAC relative to the fixed R1-FAC. The results are summarized as follows: (1) The turning point, at which the ionosphere turns from undershielding to overshielding is IR2/IR1 = 0.7 ∼ 0.8. (2) With increasing the local time deference between the R1 and R2-FAC peaks, the efficiency of the shielding by R2-FAC increases but the associated potential skews to the nightside. (3) At the same time the shielding effect is weakened around noon, where the R1-potential intrudes to the low latitude region instead, but the R2-potential remains dominant at other local times. The result suggests that the overshielding or undershielding should be identified by observations not only in a limited local time sector but also in the overall ionosphere as much as possible. In order to accurately describe the ionospheric condition, we suggest new classification terms, "complete-overshielding" and "incomplete-overshielding. " © 2012. American Geophysical Union. All Rights Reserved.

DOI： 10.1029/2012JA017669

Solar zenith angle dependence of plasma density and temperature in the polar cap ionosphere and low-altitude magnetosphere during geomagnetically quiet periods at solar maximum Reviewed

超高層物理学のための分野横断型メタデータ・データベースの構築

梅村宜生, 小山幸伸, 堀智昭, 阿部修司, 林寛生, 新堀淳樹, 田中良昌, 上野悟, 米田瑞生, 金田直樹, 元場哲郎

第4回データ工学と情報マネジメントに関するフォーラム論文集 page： A7-1 2012

N. Kitamura, Y. Ogawa, Y. Nishimura, N. Terada, T. Ono, A. Shinbori, A. Kumamoto, V. Truhlik, J. Smilauer

JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS Vol. 116 ( 8 ) 2011.8

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

We constructed an empirical model of the electron density profile with solar zenith angle (SZA) dependence in the polar cap during geomagnetically quiet periods using 63 months of Akebono satellite observations at solar maximum. The electron density profile exhibits a transition at similar to 2000 km altitude only under dark conditions. The electron density and scale height at low altitudes change drastically, by factors of 25 (at 2300 km altitude) and 2.0, respectively, as the SZA increases from 90 degrees to 120 degrees. The SZA dependence of the ion and electron temperatures is also investigated statistically on the basis of data obtained by the Intercosmos satellites and European Incoherent Scatter (EISCAT) Svalbard radar (ESR). A drastic change in the electron temperature occurs near the terminator, similarly to that in the electron density profile obtained by the Akebono satellite. The sum of the ion and electron temperatures obtained by the ESR (similar to 6500 K at similar to 1050 km altitude under sunlit conditions and similar to 3000 K at similar to 750 km altitude under dark conditions) agrees well with the scale height at low altitudes obtained from the Akebono observations, assuming that the temperature is constant and that O(+) ions are dominant. Comparisons between the present statistical results (SZA dependence of the electron density and ion and electron temperatures) and modeling studies of the polar wind indicate that the plasma density profile (especially of the O(+) ion density) in the polar cap is strongly controlled by solar radiation onto the ionosphere by changing ion and electron temperatures in the ionosphere during geomagnetically quiet periods.

DOI： 10.1029/2011JA016631