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第十五讲:外日球层鞘拾起离子与IBEX能量中性原子缎带

2022年10月24日



讲座信息

讲座题目:外日球层鞘拾起离子与IBEX能量中性原子缎带

讲座嘉宾:刘凯军(南方科技大学 教授)

讲座主持人:杨忠炜(国家空间科学中心)

时间:10月28日上午10点

地点:腾讯会议 411-8560-2478 (点此入会)

讲座摘要

Linear analysis as well as hybrid simulations are performed to examine the stability of pickup ions in the outer heliosheath. This is critical for the validity of the secondary energetic neutral atom (ENA) mechanism, a promising model for the enigmatic ENA ribbon observed by the Interstellar Boundary Explorer (IBEX). According to the secondary ENA mechanism, the ENA ribbon comes from pickup ions in the outer helioshealth after they charge exchange with the local interstellar neutrals. Since the charge-exchange time is about two years, the conventional secondary ENA mechanism needs the pickup ions to remain their velocity distribution (generally a ring-beam distribution at born) for years. On the other hand, a ring-beam velocity distribution is liable to several plasma instabilities, including the Alfvén cyclotron, mirror, and ion Bernstein instabilities. The present study evaluates how the Alfvén cyclotron instability growth can quickly scatter the pickup ions. The contributions of other instabilities are also explored. The results suggest a pickup ion scattering time on the order of 10 days, much shorter than the time scale of years needed by the conventional secondary ENA model. Discussions on the spatial retention scenario, a recent variant of the conventional secondary ENA model, are also provided.

嘉宾介绍

刘凯军,南方科技大学地球与空间科学系教授、科研副系主任。本科和硕士毕业于北京大学空间物理学专业,2007年博士毕业于美国康奈尔大学。其后分别在芬兰气象研究所和美国洛斯阿拉莫斯国家实验室从事博士后研究,并于2012年获聘为美国奥本大学物理系助理教授,后于2017年晋升为终身副教授。2018年夏回国工作,入职南方科技大学。一直从事空间等离子体物理方面的研究,其研究专长是等离子体动理学理论和计算机模拟,当前主要研究方向为地球辐射带中与等离子体动理学不稳定性相关的波动激发及粒子散射,同时关注日球层中拾起离子的动理学不稳定性过程。

 

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