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宇宙科学セミナー

 毎週木曜日の15時半より、NICT小金井本部6号館4階会議室において、宇宙科学セミナーを開催しています。 次回の予定やこれまでの発表概要については、下記をご覧ください。

次回予定

これまでの発表

2016年度

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2016/09/01 Kazumasa Iwai

New solar radio telescope at Yamagawa and Space weather forecasting
NICT developed a new solar radio telescope as a successor telescope to HiRAS in the Yamagawa radio observation facility at Kagoshima prefecture. We have completed all of developments and evaluation experiments of this new telescope, and it will be invested in our steady solar radio observation instead of HiRAS from October 1. The new telescope will be the best solar radio telescopes in the world which has much wider frequency coverage and much better time resolution than the pre-existing solar radio telescopes. This presentation summarizes the development results of this telescope and presents a plan for applying the new data to our space weather forecasting operations.
2016/07/07 Hideo Maeno

The 11th space weather users forum questionnaire result
Report the questionnaire result of 11th space weather users forum.
2016/06/30 Aoi Nakamizo

Effects of ionospheric conductivity inohomogeneiy on the magnetosphere-ionosphere convection field
The ionospheric electric potential shows global asymmetries and localized structures. Whereas these structures have been mainly discussed as the projection of magnetospheric convection, we have proposed that it can be explained also by ionospheric polarization effects due to conductivity inhomogeneities. By applying a simplified version of 'Hall-conjugate method' to a 2D ionospheric potential solver (of which concept is the same with the boundary conditions of almost all existing magnetosphere/inner-magnetosphere models), we specify one-to-one correspondence between characteristic spatial gradients of conductivity and characteristic deformations of potential. We show development plan of the magnetosphere MHD model, based on the above research, and introducing recent topics, for example, at the joint GEM&CEDAR meeting on June 19-24, 2016.
2016/06/09 Yasubumi Kubota

Polar cap potential saturation during the Bastille day storm using global MHD simulation
次世代磁気圏-電離圏結合MHDシミュレーションを用いたバスティーユイベントにおける極冠電位の飽和の研究
We are investigating the reproduction of the magnetosphere-ionosphere coupling global MHD simulation in the Bastille day storm event. Especially, we focus on the CPCP saturation and time variation. The CPCP depends on solar wind electric field, dynamic pressure and ionospheric conductivity. The conductivity of ionosphere is varied by the auroral activity in the Bastille day event . In this talk, we will discuss the effect of both the auroral conductance and solar EUV-driven conductance to CPCP saturation.

我々はバスティーユイベントのような極端現象について次世代磁気圏-電離圏結合MHDシミュレーションの再現性を調べている。特に、磁気圏-電離圏対流の基本的な物理量である極冠電位の飽和と時間変動に着目した。先行研究から極冠電位は太陽風電場、太陽風動圧、電離圏電気伝導度に依存するが、バスティーユイベントではオーロラ粒子の降り込みにより電気伝導度が大きく変動する。セミナーでは、極冠電位の飽和に対して、EUVやオーロラによる電気伝導度変化の効果について議論する。

2016/04/21 Mamoru Ishii

Current discussion for matching needs and seeds of space weather information, and establishing the hazardous map in PSTEP
宇宙天気のニーズ・シーズマッチングとハザードマップ検討の現状
One of the main theme of PSTEP is to build a dialogue system between the researchers and end users. This purpose is to provide useful information for end-users and to show new goal to the researchers with gap analysis between the cutting-edge knowledge and user needs. Now we finished the first hearing from both of researchers and users. In addition we are just drafting a framework of hazardous map for space weather phenomena. In this seminar I will present the current status of these activities and discuss future work.
PSTEPの目玉の一つに、双方向システムの構築が挙げられている。これは、最新の知見とユーザーが必要とする情報のギャップ解析を行うことで、実際に使える情報を提供すること、および研究現場に新たな目標を示すことを目的とする。現在、第1回目の両者の聞き取り調査およびギャップ解析が行われたところである。また、ハザードマップ構築についてもその骨子が固まりつつある。本セミナーでは、これらの現状について説明するとともに今後の進め方について議論する。
2016/4/14 Michi Nishioka

Proposal of ionospheric storm scales and development of ionospheric forecasting model
電離圏嵐スケールの策定とTEC予測モデルの構築
We are developing ionospheric nowcasting and forecasting systems of total electron content (TEC) for a space weather operation. Using the nowcast system, we report ionospheric conditions in the daily meeting. An universal ionospheric storm scale is used for the daily ionospheric report. Detailed explanation of the universal ionospheric storm scales is given in this talk. For the forecasting system, we are developing an empirical TEC model using artificial neural network technique. The progress of the model development is also reported.
当研究室の宇宙天気予報会議では日々の電離圏概況を報告している。我々は、宇宙天気情報としての電離圏概況をより明確に表現するため、電離圏擾乱スケールの策定を行った。また、より精度の高い電離圏予測を行うために、ニューラルネットを用いて、電離圏予測モデルの開発も行っている。本発表では電離圏擾乱スケール策定の詳細について報告し、電離圏モデルの開発状況についての報告も行う。

2015年度

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2016/03/15 Hiromitsu Ishibashi

A supplementary report on the SEALION project
A web-based realtime monitor of ionospheric disturbance in the East and Southeast Asian regions is currently under development. The prototype based on datasets of NICT's GPS-TEC and Ionosonde is open as a trial on the NICT's internal network. (http://iono-relay.nict.go.jp/iono-relay/) In this talk, while giving a brief introduction to this application, I will mention some related items: recent efforts against lightning on the SEALION project, the WONM as a centralized supporting system for operating staff, and so on. I also hope this talk will give a chance for us to deepen understanding mutual relationship among geo-scientific research, techinical development, and routine operation.
2016/02/25 Takashi Maruyama

Ionosonde tracking of infrasound wavefronts in the thermosphere launched by seismic waves after the 2010 M8.8 Chile earthquake
2010年チリ地震(M8.8)か らの地震波が励起した熱圏音波波面のイオノゾンデに よる追跡
A strong ionospheric effect was observed associated with the 2010 Chile earthquake (M8.8) in rapid-run ionograms at 1-min intervals at Kazan, Russia, ~15,000 km from the epicenter. The ionograms exhibited a multiple cusp signature that was caused by the periodic ledges of the vertical electron density distribution, which was formed by the infrasound in the neutral atmosphere through ion-neutral collisions. The heights of the density perturbation nodes that corresponded to the cusp were determined by the real height analysis of ionograms. The node heights were tracked from one ionogram to the next over a period of 15 min. By tracking the upward propagating acoustic waves, the sound speed was evaluated, which was slightly faster than that calculated using the NRLMSISE-00 model. Ionograms at higher latitudes were found to be more sensitive to thermospheric infrasound waves than previously thought. Current results showed the potential of rapid-run ionosondes (especially by the support of the VIPIR/dynasonde technique) for the application to atmospheric studies.
2010年に発生したM8.8のチリ地震に伴い、電離圏擾乱が15,000 km離れたロシアのカザンに設置されたイオノゾンデで捉えられた。1分間隔で取得されたイオノグラムを解析し、音波が電離圏高度を伝搬する様子が15分以上に亘って明らかになった。これをもとに熱圏中での音速、したがって熱圏温度を推定した。結果は、MSISモデルより若干高いものであった。高緯度では、イオノグラムが音波によるプラズマ擾乱をこれまで考えられてい た以上に高感度で捉えられることも分かった。VIPIRとダイナゾンデ技術を用いれば、地震以外の自然現象(火山噴火、オーロラ、ジェット気流、気象現象など)からの音波も捉えられる可能性があり、イオノゾンデが持つ大気研究への応用範囲が広がると期待される。
2016/02/04 Tsutomu Nagatsuma

Awareness of space environment around GEO - Toward tailored space weather forecasting -
静止軌道の宇宙環境把握 - テーラーメード型宇宙天気予報の実現に向けて-
Geostationary orbit (GEO) is one of the orbit for practical satellites for communications, broadcasting, and meteorology. On the contrary, GEO is the region for the risk of satellite anomaly, because outer radiation belt variations and substorm injectons are significantly affected in this region. The current status of tailored space weather forecasting activity will be introduced.
静止軌道は通信・放送・気象等数多くの実用衛星が利用する軌道である一方、放射線帯外帯の粒子変動、サブストームに伴う粒子注入等プラズマ環境がダイナミックに変わる領域でもあり、表面帯電や深部帯電のリスクを抱えている領域でもある。衛星障害のリスクを低減するためのテーラーメード型宇宙天気予報の実現に向けた現在の取り組みについて紹介する。
2016/01/28 Naoto Nishizuka

Development of Solar Flare Prediction Model using Machine-learning and International Situation
機械学習を用いた太陽フレア予測モデル開発と国際情勢
Solar flares have been empilically predicted based on the solar surface observations. Currently, lots of solar observation data is shared in the world, and even the huge amount of magnetogram data taken by space satellites is freely accessible. In NICT, we have developed a new prediction model of solar flares using machine-learning, which enable us to determine the prediction almost in the realtime. The similar prediction systems have already been established in other countries. In this talk, I would like to introduce our new prediction model and summarize our tasks by comparing with the internatinal situtation of flare prediction operations.
太陽爆発現象フレアは、太陽表面の観測データから経験則にもとづいて予測されてきた。一方で太陽観測データは世界中で共有され、衛星磁場観測データなど、高精度の大量のデータが利用可能になってきった。我々はこれら大量の観測データを機械学習によって解析し、リアルタイムで予報可能なシス テムの開発を行っている。同種の開発は世界各国機関で先行して行われてもいる。本セミナーでは、我々が開発を行っている予測モデルを紹介し、国際 開発・運用情勢と比較しながら、課題や問題点について議論したい。
2015/12/17 Kenro Nozaki

Numerical field strength prediction program on LF/VLF radio waves by means of wave hop theory.
波線法によるLF/VLF電界強度計算プログラム
We developed LF/VLF field strength prediction program, FS3, exactly following the ITU-R recommendations. Numerical map on the ground conductivity and permittivity is included in the program and F10.7 index is automatically obtained through the internet. Field strength is calculated for any propagation path within the ground range of 16000km for assigned day and time. We intend to revise the ITU-R recommendation based on the FS3. The algorithm of the FS3 is briefly introduced in the seminar.
ITU-R勧告を最大限に取り入れたLF/VLF電界強度計算プログラムFS3がNICTに実装された。送受信点と日時を指定すれば16000km以内のVLF~LF帯の電界強度が計算される。計算過程で必要な大地常数は内蔵の地図で、太陽活動度はF10.7を自動的に取得される。FS3を基に再度のITU勧告改訂を目指す。本セミナーではFS3の概要を説明する。
2015/12/03 Kornyanat Watthanasangmechai

Ionospheric study in Southeast Asia
Low latitudes' ionosphere often shows TEC fluctuation occurrence. A number of phenomena, such as plasma bubbles, could disrupt radio communication and GPS navigation systems. While such a system is increasingly used for critical missions i.e., aeronautical navigation, it was built without enough awareness of the ionospheric effect. To avoid unexpected scenario, the ionospheric study becomes important especially for the space weather forecast. I would like to introduce the ionospheric TEC observation system in Southeast Asia as well as some scientific results.
2015/11/26 直井 隆浩

NICT's tasks in JARE57 ----- NICTの南極行動について
I will introduce the Japan Antarctic Research Expedition (JARE) and its activity by NICT. Ionospheric observation in the Syowa station is one of the entrusted business by the Ministry of Internal Affairs and Communications. The presenter participates in the 57th Japan Antarctic Research Expedition (JARE57). I will show the concrete activities as the member, and current states of the observations for the space weather forecast at the JARE57. NICT has took part in the JARE since 1956 when the 1st JARE started. Operation and Maintenance of the instruments in the Syowa station are the main tasks for the current NICT's activities. The instruments are following; (1) the LF standard signal and time measurement on the Shirase, (2) ionosphere vertical observation and (3) GPS scintillation observation. I will introduce the general activities in JARE57 and, particularly, the current status of the GPS scintillation observation will be shown.
南極行動について示す。 NICTが総務省から委託を受ける業務として、南極昭和基地での電離層観測がある。今年度の第57次隊では、発表者が南極地域観測隊の夏隊員として参加する。観測隊員の具体的な活動を示し、宇宙天気予報に利用される情報の取得模様について紹介する。 NICTの前身である電波研究所は、1956年の第1次南極地域観測隊から電離層観測業務を実施している。南極行動での業務は計測機器の維持・運用が中心である。現在の作業対象は主に3つ、(1)「しらせ」船上での長波標準電波観測、(2)電離層垂直観測、(3)GPSシンチレーション観測、がある。本発表では、活動の全体像に加え、特にGPSシンチレーション観測について、現状と今後の発展について示す。また第IX期の南極行動の予定についても紹介する。
2015/11/19 垰 千尋

Modeling approach of magnetosphere-ionosphere-thermosphere coupling at Jupiter
木星磁気圏-電離圏-熱圏結合系のモデル研究
Jupiter and the inner part of Saturn magnetospheres create unique systems which are mainly driven by their fast planetary rotation. We developed a model which treats interactions and resulting momentum transfer among the system. I will introduce model studies including treatment of auroral process and experiments on their response to solar EUV variations.
木星や土星は、高速な惑星自転の影響が支配的な系を形成している。中性大気が持つ運動量が、衝突や電磁場による結合を通して電離圏および磁気圏プラズマの回転運動を駆動する。他方、磁気圏との結合により、熱圏・電離圏はフィードバックを受ける。この相互作用を扱う木星磁気圏-電離圏-熱圏結合系モデルについて、モデルの特徴の一つであるオーロラ電子降り込みの効果の扱いや、太陽紫外線変動に対する系の応答調査を紹介する。
2015/10/15 品川 裕之

Comments on coupling of a magnetosphere model and GAIA
磁気圏モデルとGAIAの結合に関するコメント
To numerically reproduce and predict ionospheric storms associated with geomagnetic storms, it is essential to quantitatively include the processes of electromagnetic energy input and particle precipitation from the magnetosphere into the upper atmosphere. Coupling of magnetospheric model and atmosphere-ionosphere model is a useful approach to self-consistently reproduce ionospheric storms, but there are many problems. I will present our previous studies on polar ionospheric disturbances using GAIA, and make some comments on the problems.
磁気嵐に伴う電離圏嵐をモデルで再現・予測するためには、磁気圏から超高層大気への電磁エネルギー流入と降下粒子過程を定量的に含める必要がある。磁気圏モデルと大気圏電離圏モデルの結合は電離圏嵐を再現するのに有効な手法であるが問題点も多い。本セミナーでは、これまで我々がGAIAを使って行ってきた極域電離圏擾乱の研究をまとめ、問題点についてコメントする。
2015/10/01 田 光江

Three-dimensional MHD simulation of the solar wind from the solarsurface to 400 solar radius using REPPU (REProduce Plasma Universe) code
Three-dimensional MHD simulation code, REPPU (REProduce Plasma Universe) code, is developed for modeling of space plasma phenomena, and is utilized for the solar surface and the global solar wind structure. The distinguishing features of this code is the 3-D grid system, which has no polar singularity though it is able to fit the spherical structure. We extend the outer boundary to 400 solar radius, though the previous our model covered 200 solar radius. We describe REPPU code and present several simulation results.
2015/09/17 横山 竜宏

International collaboration of ionospheric radio propagation experiment and numerical simulation of plasma bubble
国際共同電離圏電波伝搬観測計画の紹介とプラズマバブル数値シミュレーション
Two international projects of ionospheric radio propagation experiment are being planned. One is oblique sounding using ionosondes between Japan and South Korea, and the other is VHF transequatorial propagation between Japan and Australia. These projects and recent studies of plasma bubble modeling will be introduced.
2015/09/11 Nyanasegari Bhoo Pathy, Zahira Mohd Radzi / Space Science and Research Unit, ANGKASA
Introduce researches or works in ANGKASA
2015/09/13 久保 勇樹

Solar radio Observatory: Yamagawa and Hiraiso
太陽電波観測:山川と平磯
2013年度、太陽電波望遠鏡を新規開発し、山川電波観測施設に設置した。本望遠鏡は、完全な一品ものの特注品であるにもかかわらず、1年間という極めて短期間で開発したため、様々な問題点を含んだままの状態であった。そのため、現在それらの問題点の洗い出しと、調整作業を行っている。本セミナーでは、山川太陽電波望遠鏡開発の現在の進捗状況と、試験観測中に観測されたいくつかのイベントを紹介する。また、このシステムが定常運用に移行した段階で、平磯の太陽電波望遠鏡は運用を停止する予定である。そのため、平磯のこれまでの観測データについても整理が必要である。現在、平磯の太陽電波観測データについてFITS化を行っているのでそれについても簡単に触れる。
2015/07/16 中溝 葵

Researches on ionospheric electromagnetic structure by using a global ionospheric potential solver
全球電離層ポテンシャル解法を用いた電離層電流構造の研究
I have studied the ionospheric global structure by using a global ionospheric potential solver since 2010. The solver is basically the same as the so-called thin shell model (boundary condition used in existing magnetospheric MHD simulators), which solves the Poisson equation with the applied source FACs with a height-integrated ionospheric conductivity model. I will introduce the overview of the solver and ongoing researches, including (1) dawn-dusk asymmetry of global current pattern, and (2) Hall-polarization effect on potential deformations.
2015.07.09 眞柄 哲也(Kyung Hee University, Korea)

Current and future simulation researches on space weather: A bridge between theoretical modeling and observations
宇宙天気に関わる現在と将来のシミュレーション研究: 理論モデルと観測のかけ橋
Since it was discovered that solar magnetic fields produce various active phenomena such as solar flares and coronal mass ejections, numerical simulations have been a necessary as well as powerful tool to clarify dynamic processes involved in these phenomena. In this talk I report research activities of our group for the past 6 months, which have been focused on MHD modeling of solar active phenomena and its application to real events. The topics to be discussed are:
  •  ・Modeling of flare producing active-region magnetic fields
  •  ・Solar eruption model coupled with solar winds
  •  ・Interaction between a solar wind and an interplanetary coronal mass ejection
  • We show several key results from MHD simulations performed for these topics. We then discuss what have been resolved through these simulations and what are remaining issues to be clarified in future researches.
    2015.07.01 B. V. Jackson-san (University of California at San Diego, CA, USA)

    Determination of the North-South Heliospheric Magnetic-Field Component from Inner-Corona Closed-loop Propagation; Its Potential Use including in an IPS 3D-MHD Project
    From a study of non-static solar wind processes, we find that a portion of the north-south interplanetary magnetic field measured in situ near Earth is present from a direct outward mapping of fields from the low solar corona. Using the Current-Sheet Source Surface (CSSS) model (Zhao & Hoeksema, 1995), these lower coronal fields are extrapolated upward from near the solar surface. Global velocities inferred from a combination of observations of interplanetary scintillation (IPS) matched to in-situ velocities and densities measured by spacecraft instrumentation provide further outward timing assuming conservation of mass and mass flux. The north-south field component at 1AU is compared with the appropriate Advanced Composition Explorer (ACE) MAGnetometer (MAG) in-situ magnetic-field component - the Normal (RTN) Bn field coordinate - for three years throughout the Cycle 24 solar minimum. We find a significant positive correlation throughout this period between these methods of determining the Bn field compared with in-situmeasurements. This result, from a study during times when few CMEs are present, indicates that a small fraction of the low-coronal Bn component flux regularly escapes from closed-field regions. Since the Bn field provides the major portion of the Geocentric Solar Magnetospheric (GSM) Bz field component that couples most closely to the Earth's geomagnetic field, the prospects for its determination using this technique for space weather use are being actively developed by our groups.

    co-authors: H. -S. Yu, P. P. Hick, A. Buffington (Uni of California at San Diego), M. M. Bisi, (Rutherford Appleton Lab) M. Tokumaru (Nagoya Uni) J. Kim, S. Hong (SELab, South Korea)
    2015/06/25 坂口 歌織

    Prediction Model of High Energy Electron Flux in the Whole Area of Radiation Belt
    放射線帯外帯全域の高エネルギー電子フラックス予測モデルの開発状況
    an Alen Probes のデータを用いて開発している放射線帯電子フラックスの変動予測モデルについて最近の進捗状況を報告する。

    I will introduce my prediction model of electron flux in the radiation belt of magnetosphere, using the observation data of Van Alen Proves.
    2015/06/18 岩井 一正

    Solar and space weather radio sciences and the new solar radio telescope at Yamagawa
    電波観測による太陽・宇宙天気研究と山川の新太陽電波望遠鏡
    フレアに代表される太陽の爆発現象では太陽電波バーストと呼ばれる突発的な電波が放射される。電波は太陽高エネルギー粒子や衝撃波といったフレアの影響より早く伝搬する。よって太陽からの電波放射を常時モニタすることは、宇宙天気の予報にとって極めて有効である。NICTが山川に建設した 電波望遠鏡は最新のデジタル処理技術を搭載した初めての超広帯域高分解太陽電波望遠鏡である。 本講演では、近年の太陽電波研究の動向をレビュー し、新望遠鏡で計画している太陽・宇宙天気研究と現在進行中の研究状況を紹介する。

    Solar eruptive phenomena such as flares emit impulsive radio waves called a solar radio burst. Radio emission propagates faster than the effect of flares such as solar energetic particles and shock waves. Hence, a monitoring observation of the solar radio emission is very effective for the space weather forecasting. NICT has developed a new solar radio telescope at Yamagawa, which is the first super wideband high resolution solar radio telescope with latest digital technologies. This seminar reviews the recent studies on solar and space weather radio sciences and introduces the science objectives and ongoing studies of the new solar radio telescope.
    2015/06/04 陣 英克

    Validation and Update of the Whole Atmosphere-Ionosphere Coupled Model GAIA
    大気圏電離圏結合モデル(GAIA)の検証と改良
    A whole atmosphere-ionosphere coupled model, GAIA, has been developed by NICT, Kyushu University, and Seikei University. Using meteorological reanalysis and F10.7 index as inputs to the model, we have generated a simulation database of the period from 1996 to 2014. Through the comparisons of the database with empirical ionospheric and thermospheric models and observations, we have made clear which regions and periods the model cannot reproduce well. Based on the comparison results, we are currently updating the model by making more rigorous the equations and numerical methods in the GAIA's ionospheric part. As initial results, the modeled distributions of electron temperature and NmF2 seem to be much improved.

    大気圏電離圏結合モデル(GAIA)は、NICTと九州大学、成蹊大学の共同によって開発された。我々は気象再解析データとF10.7を同モデル に入力し、1996年以降 1太陽サイクル以上の長期シミュレーションを行い、データベースを構築した。これまでSSWの影響などイベントベースで 観測と比較を行ったが、本発表ではイオノゾンデや各経験モデル(IRI、MSIS、HWM)を用い、climatologicalな変動について 比較を行った。これにより、モデルが再現できていない部分の傾向が明らかになってきた(例えばSmaxのNmF2など)。観測とのずれを改善する ために、本発表ではモデル中の磁力線に沿ったプラズマダイナミクスとエネルギーの扱いを改良する試みも紹介する。初期結果では、電子温度や電子密 度分布が大きく改善することが明らかになった。
    2015/05/14 石井 守

    he preparation for JSPS Grant-in-Aid for Scientific Research on Innovative Areas (Kakenhi) application (& the report of ITU-R in April 2015)
    新学術領域検討状況 (& ITU-R報告)
    We are preparing for the final interview of the application for JSPS Grants-in-Aid for Scientific Research (Kakenhi) on Innovative Areas relating to Space Weather Forecast. I will introduce the current status of this preparation and the purpose of this study in this seminar. I also would like to introduce ITU-R conference held in Geneva in the last month.

    名大STE研等と共同で申請している新学術領域は、現在最終ヒアリングに向けた準備を行っている。本件の概要について説明する。時間があれば、ITU-Rでの検討状況についても触れる。
    2015/04/23 小川 忠彦

    Long-term occurrence characteristics of mesosphere summer echoes (MSE) observed with the Wakkanai VHF radar
    稚内VHFレーダーで観測された夏季中間圏エコー(MSE)出現の長期変化
    A 46.5-MHz VHF radar at Wakkanai (45.4 N) was operated for 9 years during 2000-2002 and 2009-2014, and often observed mesosphere summer echoes (MSE) in summer in 2000-2001 and 2009-2013. Main features of the Wakkanai MSE are as follows: Strong MSE appear at altitudes of 80-90 km, including the mesopause region around 85 km, in the daytime between the middle of June and the end of July. These fundamental characteristics are very similar to those of polar mesosphere summer echoes (PMSE) appearing at high latitudes (>60 deg.) in the NH and SH, indicating that the Wakkanai MSE are also due to very cold mesopause temperature below 150 K in summer. In this presentation, brief physical background of the MSE and PMSE phenomena and long-term occurrence characteristics of the Wakkanai MSE are discussed.

    2000年7月7日に稼働を開始した稚内(45.4N) の46.5-MHz VHFレーダーで、2000-2002年と2009-2014年の観測期間中(2003-2008年は観測停止)、2002年と2014年を除いた年の夏 季に夏季中間圏エコー(Mesosphere Summer Echoes:MSE)と呼ばれる特異なレーダーエコーが観測されてきた。稚内MSEの主な特徴は次の通りである。 1) 5月下旬から7月下旬の日中に出現するが、強いエコーは6月中旬から7月下旬に発生。 2) 出現高度は主に80 - 90 kmで、中間圏界面(高度~85 km)を含む。これらの基本的特徴は南北の極域に出現する夏 季極域中間圏エコー(Polar Mesosphere Summer Echoes:PMSE)のそれに酷似しており、MSEも夏季中間圏界面付近の温度が150 K以下に低下することが原因であると考えられる。本発表では、MSE/PMSE現象の簡単な物理的背景と、稚内MSE出現の長期変化とその原因などを議論 する。
    2015/04/16 石橋 弘光

    Treatment of Observation data in Hiraiso Solar Observatory
    平磯太陽観測施設観測データの処遇について
    Hiraiso solar observatory has been remotely operated since 2008, and we moved large amount of observation data from Hiraiso to Koganei at the end of the last year. We still have a task to classify the data, and it's essential to consider the possibility and the practical use of browsing system for it. I will introduce the current status.

    2008年度末に無人化した平磯太陽観測施設では、遠隔運用で太陽観測を行う一方で、様々な残務処理も実施し てきた。その一環として、昨年度末に大量の各種観測データを一括して小金井C2センターに移転させる作業を行った。ただし、資料分別の問 題が、先送りされた大きな課題として残されている。保存価値を巡る議論も大切だが、費用対効果の観点から保存資料閲覧システムの実現性・ 実用性について予め検討しておく事も重要であろう。発表では、本件の現状を整理して報告する予定である。
    2015/04/02 久保田 康文
    Progress Status of a Real-time Numerical Simulator using Next Generation Magnetosphere-Ionosphere Coupling Global MHD simulation.
    次世代磁気圏-電離圏結合MHDシミュレーションのリアルタイム化の進捗状況
    We are developing a real-time numerical simulator using next generation magnetosphere-ionosphere coupling global MHD simulation. The feature of simulation has an advanced robustness to strong solar wind case. In this talk, I will introduce a few events including a strong solar wind case and discuss the problem.

    我々は太陽風データをインプットとした、次世代磁気圏-電離圏結合MHDシミュレーションのリアルタイム化を行っている。以前NICTで運用して いたリアルタイム磁気圏シミュレーションはコードにロバスト性がなく極端な太陽風の場合には上限値を決め、インプットとなる太陽風の大きさを制限 していた。本発表では、ロバスト性が高くなった新コードで実際の太陽風データをインプットとして極端イベントも含めた数例のシミュレーションを 行ったので、その結果を紹介し問題等を議論する。

    2014年度

    タイトルクリックで概要表示
    2015/03/19 西岡 未知

    What is the best definition of TEC quiet-day and disturbed-day?
    「TEC静穏/擾乱日の定義について
    We are developing Total Electron Content (TEC) prediction model using TEC observation data over Japan. In this talk, I will introduce the progress of our study.

    日本上空の電離圏全電子数(TEC)予測の実現に向け、GEONETによる日本上空の電離圏全電子数(TEC)観測データを用いたTEC経験 モデ ル構築を進めている。 本発表では、モデル構築の進捗状況を報告する。
    2015/03/12 Suhaila Binti M Buhari

    A statistical study of equatorial plasma bubble observed by high-density GPS receivers in Southeast Asia over the years 2008 -- 2013 (PhD final examination)
    Equatorial plasma bubbles (EPBs) were investigated using two-dimensional maps of rate of total electron content change index (ROTI) from 127 GPS receivers in Southeast Asia with an average spacing of about 50--100 km. 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 occurrence of successive EPBs along the 96^o E -- 120^o E longitude was normally seen during the passage of the solar terminator in the equinoctial months. In this study, we present the occurrence rate of isolated EPB versus the successive EPB along the geographical longitudes of 96^o E -- 120^o E during a half of solar cycle period (2008 -- 2013). We examined the occurrence of EPB by the amplitudes of ROTI which is larger than 0.1 TECU/min for every 2^o longitudes sector along the 96^o E -- 120^o E. The isolated (successive) EPB was determined by the occurrence of EPB in any (all) 2^o longitudes sector(s) along the 96^o E -- 120^o E. Although the occurrence of the successive EPB along the 96^o E -- 120^o E exhibits high correlation with the solar activity, the occurrence rate of isolated EPB does not strongly depend on the solar activity. The high occurrence rate of isolated EPB within 96^o E -- 120^o E is due to the broad geographical coverage and it tends to extend in all longitude sectors during the high solar activity. The high occurrence rate of the isolated EPB cannot be captured by a single GPS receiver because of small geographical coverage or in-situ satellite measurement where sometimes flying too high to detect the EPB at lower altitudes.
    2015/02/19 亘 慎一

    リアルタイム太陽風データの受信について
    Reception of real-time solar wind data
    ACEの後継機となるDSCOVRが2015年2月11日に打ち上げられ、長期的に安定して太陽風データを入手できるようになった。リアルタイム 太陽風データ受信、DSCOVRのデータの概要、長期的な太陽風の変動などについて紹介する。
    2015/02/05 飯田 佑介:ISAS/JAXA

    画像自動認識手法を用いた太陽表面対流による磁極輸送解析
    The analysis of the magnetic flux transport by the solar surface convection based on the auto-recognition technique
    今日得られる大量の衛星観測太陽画像データを統計的に解析処理するには、画像動認識手法が有効である。また太陽表面は乱流的で短時間に変化するが、この対流と磁気要素(小規模黒点)の運動を理解することで太陽ダイナモを理解することもできる。セミナー前半では、現在開発している太陽物理 版・画像自動認識手法を紹介し、次に太陽磁場輸送と太陽ダイナモに応用した結果について紹介する。
    2015/01/29 丸山 隆

    「子午面内電離圏観測ネットワークによる低緯度電離圏高度の変動 -Ionospheric Ceilingの形成」
    Low-latitude Ionospheric Height Variation as observed by Meridional Ionosonde Chain: Formation of Ionospheric Ceiling over the Magnetic Equator
    We present an analysis of the influence of the fountain effect on the hmF2 in the trough region of the equatorial ionosphere, on and off the magnetic equator. This study uses observations from a chain of ionosondes in the Southeast Asian sector to examine the seasonal, latitudinal, and local time variations in the hmF2. We pinpointed a particular characteristic (which we call the "ionospheric ceiling") that consists of a near-constant hmF2 at the magnetic equator in the late morning and early afternoon. They we use SAMI2 to explore the reason behind the formation of this "ceiling" (the field-aligned plasma diffusion caused by the fountain effect). The implications of the "ionospheric ceiling" for the modeling community are briefly touched upon, and the dangers of using the equatorial hmF2 as a proxy for ExB are emphasized.
    2015/01/20 眞柄 哲也 / An Jun Mo (Kyung Hee University)

    太陽磁力線の現在と今後のシミュレーション研究:浮上、組織化、拡散、そして最終的に太陽からの噴出
    Current and future simulation researches on a solar magnetic field:it emerges, organizes, dissipates and eventually erupts from the Sun
    Since it was discovered that a solar magnetic field shows very dynamic behavior, numerical simulations have been a necessary as well as powerful tool to clarify time-dependent processes of a solar magnetic field. In this talk I introduce research activities in our group investigating various time-dependent processes of a solar magnetic field. The topics are: (i) Emergence of magnetic fields into the solar atmosphere (flux emergence) (ii) Formation of magnetic structures in the solar atmosphere (prominences/filaments, sigmoids) (iii) Dissipation of magnetic fields in the solar atmosphere (flares, jets, coronal heating) (iv) Ejection of magnetic fields toward the interplanetary space (solar winds, coronal mass ejections).
    2015/01/15 長妻 努

    Himawari/SEDAによる日本上空の宇宙環境モニタリング・予測
    Monitoring and Forecasting of Space Environment by Himawari/SEDA
    Space Environment Monitor (SEDA) was installed at new Japanese Meteorological Satellite, Himawari-8. Results of initial observation and a plan of a space environment monitoring and forecasting platform will be introduced.
    2014/12/18 西塚 直人

    0.8-4.5 GHz周波数帯における太陽電波バーストの統計解析
    Statistical Analysis of Solar Radio Bursts in the frequency range of 0.8-4.5 GHz
    I had visited Ondrejov observatory in Czech Republic for totally 4 months, where I analyzed radio spectra of solar flare bursts. The observing frequency range is 0.8-4.5 GHz, which overlaps the observation frequency ranges of Hiras and Yamagawa solar observation systems. Fast accelerated electron beams generated in a solar flare excite plasma waves and then radiate radio pulses. Some-times, radio pulses are observed between two common frequencies in a short time period (~10 s), and the two upper and lower frequencies comove gradually upward or downward in frequency. This is called ``Slowly Drift Pulsating Structure (DPS)'', which may help us to understand the fundamental process of the generation of high energy electrons. In this talk, I will introduce my result of analysis of 106 events observed during 2002-2012, focusing on the correlation between DPSs and hard X-ray bursts, the relationship between DPSs and the solar activity in this cycle, and the histograms of several physical parameters by assuming solar atmospheric models. The similar observations are possible with Yamagawa solar observation system, and I would like to discuss the application to Yamagawa with everyone.
    2014/12/11 山本 和憲

    太陽地球大気の地上多点観測データの解析ソフトウェア(TDAS/UDAS)ワークショップ
    Workshop on Analysis Software (TDAS/UDAS) for Multipoint Ground-based Observation Data of Solar-Terrestrial Phenomena
    IUGONET project and ERG science center are developing the data analysis software called TDAS/UDAS in cooperation with each other. A workshop on the comprehensive analysis of multipoint ground-based observation data of the solar-terrestrial phenomena was held in August, where the usage of the TDAS/UDAS was well introduced. I attended the workshop, and I would like to introduce how to use TDAS/UDAS in this seminar.
    2014/11/20 田 光江

    磁気圏尾部リコネクションモデルに依存するサブストームのグローバル構造
    Global Structure of Substorm depending on Magnetotail Reconnection Model
    We carry out the substorm simulation using a global magnetohydrodynamic code with an effective resistivity model evaluated in the study of the anomalous resistivity induced in the instability occurring during the wave-particle interaction in microscopic scale. We present the simulation results of phenomena in the substorms, such as the flux rope formation and the Aurora Electro Jet indices, in which substorm onsets can be clearly seen. We also investigate the applicability of the present effective resistivity model by comparing those results with those obtained from the other effective resistivity models, e.g. steady collisionless driven reconnection resistivity model, and the constant resistivity model.
    2014/11/13 北内 英章

    南極観測船「しらせ」船上、長波標準電波計測とITU-R SG3での報告
    Report of ITU-R SG3 on Measurements of Standard Long-Wavelength Radio Emission on Japanese Antarctic research ship "Shirase"
    We attend Japanese Antarctic research expedition for ionosphere steady observations, and on Japanese Antarctic research ship ``Shirase'' we receive and measure the field strength of standard long-wavelength radio emission. In this year, we submitted a paper on the measurements to ITU-R (International Telecommunication Union - Radiocommunication Sector -Study Group 3: ITU-R SG3) held in Geneva in September. In this seminar, I would like to introduce my paper and chairman's report in ITU-R.
    2014/10/23 Suhaila B. M. Buhari

    東南アジアの赤道域プラズマバブルの観測
    The observation of equatorial plasma bubble in Southeast Asia
    Equatorial plasma bubbles (EPBs) are three-dimensional structures of depleted plasma density that are often observed in the nighttime equatorial ionosphere. They are initiated near the magnetic dip equator, in the bottomside of the F layer, and develop with time, upward in altitude and poleward in latitude (into both hemispheres), taking the form of longitudinally-narrow, vertically-extended wedges that penetrate deep into the topside of the F layer. Moreover, these structures drift zonally as they evolve in time. Much of what is not yet known about EPBs stems from our inability (1) to capture spatial descriptions of these structures, and (2) to monitor their evolution as a function of time. In this seminar, the two-dimensional maps of equatorial plasma bubbles (EPBs) using high-density GPS networks in Southeast Asia will be presented. The EPBs were investigated using two-dimensional maps of the rate of TEC change index (ROTI) acquired from 127 GPS receivers in SEA with an average spacing of about 50 - 100 km. We will present results from a case study on 5 April 2011 in which 16 EPBs were detected in longitude and tracked in time. The observation of EPBs by GPS ROTI measurement coincided with the depletions of 630-nm emission of the airglow imager and ion density from the C/NOFS satellite. The EPBs observed by GPS ROTI measurement survived longer than 3-m-scale irregularities observed using the Equatorial Atmosphere Radar (EAR). The occurrence rate of EPB in Southeast Asia will be briefly presented. The day-to-day variability of the occurrence of EPB in Southeast Asia over an extended longitude sector (90 to 120 degrees, East longitude) will be discussed.
    2014/10/16 横山 竜宏

    電離圏擾乱現象の数値モデリング
    Numerical modeling of ionospheric irregularities
    Irregularly structured ionospheric regions can cause diffraction and scattering of trans-ionospheric radio signals. These signals present random temporal fluctuations in both amplitude and phase, which is known as ionospheric scintillation. Especially, plasma density depletion in the equatorial region, a so-called plasma bubble, causes a severe scintillation and navigation outage. Modeling effort for the ionospheric irregularities such as plasma bubble will be presented.
    2014/10/02 久保 勇樹

    太陽電波観測と宇宙天気予報への応用
    Solar radio observation and its application to space weather forecast
    1. Introduction of solar radio bursts
    2. Solar radio telescope at Yamagawa
    3. Application of solar radio observation to space weather forecast
    2014/09/25 坂口 歌織

    静止軌道における放射線帯電子フラックス予測の現状と中軌道予測に向けた検討
    Current status of radiation belt electron flux prediction at GEO and considerations of application to MEO
    We developed a prediction model of the radiation belt electron flux at geostationary earth orbit (GEO). The model is based on the multivariate autoregressive model and Kalman filtering method. We will report the latest validation result of GEO prediction and examination results for the application to modeling at medium earth orbit (MEO).
    2014/09/18 Tiar Dani / Jiyo (LAPAN)

    1. Solar Flare Prediction Based On Sunspot Physical Parameters
    2. Declining Trends of Global Upper Atmospheric Density during the 23rd Solar Cycle
    3. Ionospheric Research and Application for Communication and Navigation in Indonesia
    1. Flare activities had strong relationships with magnetic field. Changes in the structure and connections of these fields over the sunspot had probability on flare occurring. One way to predict flare is by observing sunspot. Sunspot as an indicator on solar activities is the easy part to observe. By observing sunspot, we obtain physical parameter of sunspot group such as McIntosh classification system. Solar flare related to sunspot and can be used to predict flare. LAPAN's X-Ray Flare Prediction Software had been developed based on the Backpropagation Artificial Neural Network. This software using sunspot physical parameters input such as McIntosh Classification Value, daily sunspot number, sunspot area in millionth solar hemisphere and sunspot position on the sun disk. The software gives result in lowest and highest x-ray flare type that might be occurred. This prediction valid for 24-hours after the observation conducted.

    2. In this study, we obtained the upper atmospheric density trends by using orbital element data of 52 LEO satellites at height range of 400-800 km during the 23th solar cycle (1996-2008). Globally, the upper atmospheric density experienced declining trend during solar cycle 23 with a gradient of 1.13x10^{-5}. Each atmospheric density obtained from all 52 satellites is also showing declining trends consistency in terms of atmospheric density scale height. This declining trend in upper atmospheric density will decrease with the increasing of altitude with a gradient of 6x10^{-6}. The decreasing atmospheric density in the upper atmosphere is believed to be related to the low solar activity in each cycle by decreasing the solar EUV flux radiation that interacts with the atoms and molecules in the atmosphere. It is also suspected that the increasing greenhouse gases will cause atmospheric density to decline through a cooling effect in the upper atmosphere.

    3. The study of the ionosphere is the part of space weather research conducted at the Space Science Center. Research topics include the dynamics of the ionosphere for communications and navigation, modeling, and applications for radio communications and navigation systems. Six ionosondes, four GISTM (GPS Ionospheric Scintillation and TEC Monitor), and eleven ALE (Automatic Link Establishment) system have been operated for that purpose. Some of the results are long-term variations of the ionospheric layer base on the critical frequency and scintillation index, a simple model of low latitude ionosphere of Indonesia (Muslim et al), model of scintillation events (Asnawi et al), and the index of regional ionosphere Indonesia (Suhartini et al). Application of the results of research conducted through off-line and on-line information services. Off-line services such as quarterly HF prediction and regional ionospheric index. Monthly prediction of base-to-base and base-to-area HF circuits, maps of critical frequency (foF2), and maps of Total Electron Content, are delivered via Lapan website (www.lapan.go.id). In addition, the Center also conducted technical training and the dissemination.
    2014/08/28 小川 忠彦

    巨大竜巻による電離圏擾乱:HFレーダーとGPS-TECの同時観測結果
    Simultaneous Observations of Ionospheric Disturbances by Giant Tornadoes with HF-radar and GPS-TEC
    Three giant tornadoes occurred at Tsukuba, Ibaraki on 2012 May 6, at Moore, OK in US on 2013 May 20 and at El Reno, OK in US on 2013 May 31. From the GPS-TEC data (total number of electrons), Nishioka et al. (2013) have discovered concentric waves in the ionosphere at around Moore tornado, showing that a severe meteorological event causes atmospheric waves propagating upward in the upper atmosphere and reaches the ionosphere.
    In this talk, I will show the results of simultaneous observations of the ionospheric disturbances by the SuperDARN high-frequency (HF) radar and the GPS-TEC in the above three tornadoes. The main properties of the waves by TEC and HF-radar observations are as follows:
    (1) the same patterns of concentric waves at around the tornadoes.
    (2) the durations are <7 hrs,
    (3) the propagation velocities are 120-270 m/s, the periods 10-20 min., and the wavelengths 140-300 km. These results may contribute to reveal the coupling process of the upper/lower atmospheres.
    2014/08/21 Nanan Balan
    Space Weather and its relevance to the High-Tech society
    Thanks to the works of a number of scientists it is known that severe space weather can cause extensive social and economic disruptions in the modern high-tech society. For example, an event such as the Carrington event of 1859 at present times would cause serious damages with prices between one trillion and two trillion US Dollars. However, what determines the severity of space weather and whether it can be predicted are not yet know. The seminar will address these questions and the science of severe space weather.
    2014/07/17 石橋 弘光

    SEALIONの活動報告:雷への最近の対抗処置
    Activity Report on the SEALION: Recent efforts against Lightning
    The lightning protection in the monsoonal region of south-east Asia is one of the most important matters we have to deal with. At this moment, the ionosonde observations in Chiang Mai, Chumphon and Kototaban sites are stopped. While we have frequently damaged from lightning strikes, we repeat the same thing, like a game of cats and mice. In all the sites of SEALION, we have installed various instruments for lightning protection: lightning transformers for the power line, SPD (surge protective devices) for co-axial connectors, intelligent UPS for PCs, and so on. We are forced to handle the ground earthing methods on a case-by-case basis, becasue the earthing environment is quite different at each site. In this talk, I will present our recent efforts at lightning protection with a new surge protection approach.
    2014/07/10 Yeon Joo Lee (ISAS)
    Long-term variations of UV reflectivity of Venus, and a possibility of influence from the 11-year solar activity cycle
    The UV wavelength observation has been detected dark and bright features over the globe at the Venus cloud top level (65-70 km altitudes), since its discovery in 1920s. Dark features are caused by absorption of an unknown UV absorber, which is located within the upper cloud layer, and bright are caused by scattering effects of the clouds and haze aerosols. Strong horizontal winds near cloud top changes cloud morphology in a few days. The sulfuric acid aerosol particles in the haze and clouds take part in sulfur photochemical processes. Therefore, the features shown in the UV images are strongly associated with atmospheric dynamics and chemistry of the Venus mesosphere.
    We analyzed the Venus UV reflectivity observed by the Venus Monitoring Camera on board Venus Express, ESA's mission toward Venus. First we studied about photometric correction methods to retrieve albedo values. Then, this albedo is used in our data analysis for a number of images obtained from 2006 to 2011. We found that the global mean albedo decreased significantly by 20-30% over time. This trend is driven by a decrease in albedo at high latitudes. We showed that the temporal variation of the latitudinal UV contrasts is correlated with mesospheric SO2 abundance. We suggest that meridional transport of SO2 affects the upper haze formation at high latitudes. Additionally, we introduce a possibility that the 11-year solar activity cycle might affect the UV contrasts in the Venus mesosphere.
    2014/07/03 海老原 祐輔

    サブストーム直後に現れる過遮蔽の数値実験
    内部磁気圏の対流電場はリングカレントの発達やプラズマ圏の形成を促す上で重要な役割を果たす。ところが、サブストームの直後、対流電場の極性が反転する事象が幾つか報告されている。過遮蔽現象と呼ばれるこの現象を電磁流体シミュレーションによって再現することができた。シミュレーション結果は極冠域、オーロラ帯、中緯度、磁気赤道の地磁気変化の特徴をよく再現する。本セミナーではサブストーム時に現れる過遮蔽のメカニズムとその高エネルギー粒子環境への影響について報告する。
    2014/06/26 陣 英克

    電離圏データ同化モデルの開発に向けて
    我々は、これまで大気圏電離圏結合モデル(GAIA)を開発してきた。そして、将来的な数値予測の実現に向け、モデルに観測データを融合しようとしている。本発表では、既に取り組んでいるGAIAへの 気象データの同化(入力)について振り返ったのち、 電離圏観測をどのように同化するべきか検討する。そして、NCARのデータ同化システムについて紹介し、今後のGAIAのデータ同化の戦略を議論する。
    2014/06/19 久保田 康文

    グローバルMHDシミュレーションを用いたKH不安定が引き起こすULF波動の解析
    ULF波動は放射線外帯電子の加速に大きな役割を果たすと考えられている。ULF波動生成の要因の一つとしてKH不安定が考えられる。次世代磁気圏-電離圏結合シミュレーションでは、解像度が向上したため磁気圏境界でKH不安定が再現されている。また、KH不安定にともない、地上や磁気圏でULF波動も引き起こされている。 本発表ではシミュレーションからKH不安定で引き起こされる磁気圏-電離圏のULF波動についてスペクトル解析を行った。初期結果ではあるが、ULF波動の太陽風速度依存性、IMF依存性について紹介する。今後、観測との比較や放射線帯モデルに使用する可能性について議論をしたい。
    2014/06/12 Roland T. Tsunoda (SRI International, USA)
    Collaborative Study of Large-Scale Wave Structure (LSWS)and Development of Equatorial
    Plasma Bubbles (EPBs)
    A research topic of considerable interest, to scientists atboth NICT and SRI International (SRI), is the day-to-dayvariability in the development of equatorial plasma bubbles (EPBs)in the nighttime equatorial F layer.Generally speaking, EPBs areof interest because they often contain steep gradients and intenseirregularities in plasma density that can affect communication andnavigation systems that use trans-ionospheric propagation paths.With an improved understanding of the underlying physics that controlsday-to-day variability, a goal would be to be able to implement ashort-term forecasting capability, for example, for space-weatherapplications.In this seminar, we will present a brief discussion of the rolethat large-scale wave structure (LSWS) appears to be playing inthe development of EPBs.We then explain why a comprehensivedescription of LSWS has yet to be compiled.Without knowledge ofits properties, we remain unable to uncover the details of how LSWSaffects EPB excitation, growth, and evolution.We close the seminarby discussing the opportunities for highly productive research thatcan be pursued through collaborative research between NICT and SRI.The most interesting results are likely to come from a joint analysisof the data collected by both space-borne and ground-based sensors inSEALION and the rest of Southeast Asia, as well as those in the Pacificsector.
    2014/06/05 石井 守

    宇宙天気をめぐる国際動向
    近年、ICAOのAnnex3(航空運用における気象情報)改訂で宇宙天気情報が使用されることになるなど、宇宙天気の実利用化が活発化している。現在NICTが関係している国際宇宙天気動向として、ISES・ICTSW・CGMS・COPUOSおよびITU-R等の関係と動向について説明する。
    2014/05/22 丸山 隆
    2011年東北地方太平洋沖地震による電離圏擾乱(続報)
    この地震では、これまでに様々な電離圏擾乱が報告されているが、擾乱の現れ方には多くの疑問点が残されていた。地震計のデータを元にイオノグラム上に観測された波動現象と地震波とを対比させるとともに波動シミュレーションを行い、定量的な解析を行った。3月9日の前震によっても明瞭な電離圏擾乱が観測され、また本震に伴って観測された擾乱はこれまで言われていたようなレーリー波ではなくP波とコーダ部分によることも判明した。併せて、ロシアのタタールスタンで観測された同様なデータも紹介する。イオノグラム上の擾乱は、これまで考えられていたような稀な現象ではないことも分かった。
    2014/05/15 亘 慎一

    Stealth CMEについて
    極端紫外線やコロナグラフによる宇宙からの太陽観測の充実は、現状の観測装置では対応するはっきりとした太陽面の活動が観測されないCMEの存在を明らかにした。このようなCMEは'Stealth CME'と呼ばれており、宇宙天気予報においてその地球への影響を予測するのが難しい現象となっている。サイクル24では、その活動が低いこともあり、このようなCMEによる地磁気擾乱がしばしば観測されている。
    2014/05/08 長妻 努

    NICTにおけるジオスペース研究の現状と今後
    今中期、NICTではジオスペースの研究課題として、静止軌道における宇宙環境(サブストーム粒子、放射線帯粒子)の予測に関する課題に取り組んできました。本セミナーではこれらの現状を概観すると共に、次期中期に向けた方向性についての検討・議論のきっかけとなる話をしたいと思います。
    2014/04/17 西塚 直人

    太陽大気におけるフラクタル・リコネクションと粒子加速
    Recent space solar observations, such as Hinode, SDO, STEREO and RHESSI,have revealed that magnetic reconnection is ubiquitous in the solarcorona and chromosphere, ranging from small scale (nanoflares) to globalscale (CME related flares). These reconnection events are oftenassociated with mass ejections with various sizes. This implies that themagnetized solar atmosphere consist of self-similar structure, i.e.,fractal structure and dynamics. Bursty radio and hard X-ray emissions insolar flares also suggest fractal-like time variability of reconnectionand associated particle acceleration. Recent theoretical studies haverevealed that multiple plasmoids make a current sheet turbulent in 3Dand enable intermittent ejections and their interactions. In such aprocess, particles are accelerated at multi X-lines with locallyenhanced electric field and at multiple shocks collided by plasmoids.High resolution observations have also discovered small scale structuresof a current sheet, i.e. multiple plasmoids. They show the slow risingmotion in pre-flare phase and strong acceleration during impulsive phaseassociated with hard X-ray bursts, indicating particle accelerationoccurring at the same time. Plasmoid ejections are observed to increasereconnection inflow and reconnection rate. The similar phenomena havebeen discovered in laboratory experiments, in which a plasmoid ejectionincreases reconnection electric field in a current sheet. Furthermore, alarger plasmoid ejection induces stronger electric field. These areevidence of plasmoid-induced-reconnection, and in a fractal currentsheet this process can repeat several times. We will discuss recentobservations and theories related to fractal reconnection and plasmoids,and discuss possible implication to reconnection physics and particleacceleration in solar flares.
    2014/04/10 Suhaila M. Buhari
    Two-dimensional structure of equatorial plasma bubbleobserved using GPS networks in South East Asia region
    We present the two-dimensional structure of EPBs observed using GPSnetworks over South East Asia (SEA) region. GPS data used in this studywere obtained from Malaysia Real-Time Kinematics network (MyRTKnet),International Ground Station (IGS) and Sumatera GPS Array (SUGAR) networks.MyRTKnet, IGS and SUGAR networks is located at equatorial region and has127 receiver stations across South East Asia with average spacing between50 - 100 km. Two-dimensional maps of rate of TEC index (ROTI) has beenconstructed from all visible GPS satellites in SEA region in order todetect the occurrence of EPB in 2011. The characteristics of EPB in 2011will be discussed.
    2014/04/03 西岡 未知

    ニューラルネットワークを用いた日本上空電離圏全電子数モデルの構築
    日本上空の電離圏全電子数(TEC)予測の実現に向け、GEONETによる日本上空の電離圏全電子数(TEC)観測データを用いたTEC経験モデル構築を進めている。本発表では、モデル構築の進捗状況を報告する。
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