日本地球惑星科学連合2019年大会

講演情報

[E] ポスター発表

セッション記号 P (宇宙惑星科学) » P-EM 太陽地球系科学・宇宙電磁気学・宇宙環境

[P-EM11] Dynamics of Magnetosphere and Ionosphere

2019年5月29日(水) 13:45 〜 15:15 ポスター会場 (幕張メッセ国際展示場 8ホール)

コンビーナ:中溝 葵(情報通信研究機構 電磁波研究所)、尾崎 光紀(金沢大学理工研究域電子情報学系)、藤本 晶子(九州工業大学)、堀 智昭(名古屋大学宇宙地球環境研究所)

[PEM11-P12] Flow speed dependence of ion temperature, electron temperature, and their ratio in the near-Earth magnetotail reconnection region

*渡邊 香里1星野 真弘1桂華 邦裕1斎藤 義文2北村 成寿1 (1.東京大学、2.宇宙航空研究開発機構・宇宙科学研究所)

キーワード:温度比、フロー、MMS

Plasma in the Earth's magnetotail are heated up to 1-10 keV and stored in the plasma sheet. One of the heating or acceleration mechanisms is the magnetic reconnection. Heated or accelerated plasma are transported both earthward and tailward as fast flow with a speed of several hundred kilometers per second. However, what determines the partition among ion and electron thermal energy and kinetic energy is an unresolved problem. It has been reported that ion temperature Ti, electron temperature Te, and their ratio Ti/Te vary spatially and depend on the conditions of fast flows [Wang et al., 2012, Runov et al., 2018] but there are few studies which focus on macroscopic profiles of them in reconnection regions in the magnetotail.
In this study, we examine the relation between flow speed and average profiles of Ti, Te, and Ti/Te in the magnetotail reconnection region by using data obtained from FPI and FGM on board the MMS spacecraft. We use the observations for a period from May to August 2017 and take out the data in the region of XGSM < -15 Re, -10 Re < YGSM< 10 Re, and beta > 0.1. We then divide them into different groups according to flow speed normalized by alfven speed and show Bz/Blobe– Bx/Blobe maps of Ti, Te, and Ti/Te of each group.
The results show that ion temperature increase with increasing flow speed while electron temperature decrease. Ion temperature are hotter around the X-point. The structure of inflow and outflow regions is pronounced in the profile of electron temperature. Ti/Te in inflow region are greater than in outflow region, which means that ion and electron temperatures become comparable by passing through the diffusion region. The results suggest that electron get less energy when more energy is partitioned into plasma kinetic energy. We will discuss about the profiles of anisotropy of plasma temperatures to know more details about the heating mechanisms.