伴随等离子体密度下降的磁声波与辐射带电子的波粒相互作用及其散射效应  

Scattering of radiation belt electrons caused by wave-particle interactions with magnetosonic waves associated with plasma density drop

作　　者：顾旭东[1] 何颖 倪彬彬[1,2] 付松[1] 花漫[1] 项正 GU XuDong;HE Ying;NI BinBin;FU Song;HUA Man;XIANG Zheng(School of Electronic Information,Wuhan University,Wuhan 430072,China;Center for Excellence in Comparative Planetology,Chinese Academy of Sciences,Hefei 230026,China)

机构地区：[1]武汉大学电子信息学院,武汉430072 [2]中国科学院比较行星学卓越创新中心,合肥230026

出　　处：《地球物理学报》2020年第6期2121-2130,共10页Chinese Journal of Geophysics

基　　金：国家自然科学基金(41574160,41674163);湖北省自然科学优秀青年基金(2016CFA044);中国航天局预研项目(D020303,D020308);澳门科技大学月球与行星科学实验室和中国科学院月球与深空探测重点实验室伙伴实验室开放课题共同资助

摘　　要：利用范阿伦卫星的高质量观测数据,我们报道了伴随等离子体密度下降的磁声波现象.通过选取分别发生于2013年7月26日(事件A)和2013年9月19日(事件B)的两个相应事件进行细致分析,我们开展试验粒子模拟计算了磁声波对辐射带电子的散射系数,并求解二维福克-普朗克扩散方程量化了磁声波散射导致的辐射带电子动态变化.结果表明,事件A中的磁声波的散射作用主要发生于投掷角范围为60°~80°、能量范围为20~200keV的辐射带电子,而事件B中的磁声波的散射作用主要发生于投掷角范围为50°~80°、能量范围为20~400keV的辐射带电子;两个事件中的磁声波均能导致辐射带电子的蝴蝶状投掷角分布,但是由于事件B的磁声波幅度更强,形成的电子蝴蝶状分布更明显.Using high quality Van Allen Probes data,we report a type of magnetosonic(MS)waves occurring concurrently with the ambient plasma density drop.We select two representative events observed on 26 July 2013(Event A)and 19 September 2013(Event B)for a detailed analysis.In terms of computing electron diffusion coefficients via test particle simulations and numerically solving the two-dimensional Fokker-Planck diffusion equation,we quantitatively investigate the scattering effect of this type of MS waves on the temporal evolution of radiation belt electron distribution.The results indicate that the MS waves associated with the density drop can cause considerable pitch angle and momentum diffusion for radiation belt electrons at energies of 20~200 keV and equatorial pitch angles of 60°~80°for Event A,and for electrons at energies of 20~400 keV and equatorial pitch angles of 50°~80°for Event B.For both events,butterfly pitch angle distributions of radiation belt electrons can be formed under the impact of the observed MS waves,while the electron butterfly distribution tends to be more pronounced for Event B due to stronger MS wave intensity.

关 键 词：等离子体密度 磁声波 散射效应 蝴蝶状投掷角分布 

分 类 号：P354[天文地球—空间物理学] P353[天文地球—地球物理学]