[P-EM12] Dynamics of the Inner Magnetospheric System

[PEM12-P16] Statistical Analysis of Latitudinal Electron Density Distribution in the Plasmasphere

*半原 綾乃¹、尾花 由紀²、宮下 幸長^3,4、新堀 淳樹⁵、大塚 雄一⁵、熊本 篤志⁶、土屋 史紀⁷、松田 昇也⁸、松岡 彩子⁹、笠原 禎也¹⁰、三好 由純⁵、篠原 育⁸、William Kurth¹¹、Craig Kletzing¹¹、Charles Smith¹²、Robert MacDowall¹³ (1.大阪電気通信大学大学院工学研究科工学専攻先端理工学コース、2.大阪電気通信大学工学部基礎理工学科、3.韓国天文研究院、4.韓国科学技術聯合大学院大学校、5.名古屋大学宇宙地球環境研究所、6.東北大学大学院理学研究科地球物理学専攻、7.東北大学大学院理学研究科惑星プラズマ・大気研究センター、8.宇宙航空研究開発機構 宇宙科学研究所、9.京都大学 理学研究科 地磁気世界資料解析センター、10.金沢大学総合メディア基盤センター、11.Department of Physics and Astronomy, University of Iowa、12.Institute for the Study of Earth, Oceans, and Space, University of New Hampshire、13. Solar System Exploration Division, Goddard Space Flight Center)

キーワード：プラズマ圏、磁気圏電離圏結合

Plasma density distributions along magnetic field lines give important information on plasma supply mechanisms from the ionosphere.However, most observations so far are biased near the equatorial plane; there have been few observations which give information on the density along field lines.The geospace exploration satellites Arase and Van Allen Probes(RBSP) have orbital inclinations of about 31 and 10 degrees, respectively.These satellites sometimes fly at different latitudes on the same field line, simultaneously.Using such conjunction data, the field aligned profile of the electron density can be estimated.
The electron densities were calculated from the Upper Hybrid Resonance frequencies obtained by HFA / PWE onboard Arase or the EMFISIS Waves instrument onboard RBSP.In this study, we assumed a power-law density model in which the density decreases with the m_th-power of the geocentric distance by comparing electron densities at Arase and RBSP-A or B.
At this moment, the conjunction events on April 5, 2017 were analyzed, and the following results were obtained.For flux tubes of 3.20 The expected power-law index m depends on the plasma supply model. In the collisionless models, m is close to 4.On the other hand, in the diffusive equilibrium model, close to 0.5∼1.So our results suggest that the plasmasphere is in diffusive equilibrium.
In this presentation, we will introduce further results and discuss the plasma supply mechanism.