磁暴期间辐射带电子相空间密度的多卫星联合观测  

Multi-satellite observations of storm-time radiation belt electron phase space density variations

作　　者：刘泽源 倪彬彬[1,2] 付松[1] 项正[1] 郭建广 曹兴 顾旭东[1] 易娟[1] 郭英杰[1] 郭德宇 王敬之 LIU ZeYuan;NI BinBin;FU Song;XIANG Zheng;GUO JianGuang;CAO Xing;GU XuDong;YI Juan;GUO YingJie;GUO DeYu;WANG JingZhi(School of Electronic Information,Wuhan University,Wuhan 430072,China;Chinese Academy of Sciences Center for Excellence in Comparative Planetology,Hefei 230026,China;Key Laboratory of Space Weather,National Center for Space Weather,China Meteorological Administration,Beijing 100081,China)

机构地区：[1]武汉大学电子信息学院空间物理系,武汉430072 [2]中国科学院比较行星学卓越创新中心,合肥230026 [3]中国气象局国家空间天气监测预警中心,北京100081

出　　处：《地球物理学报》2020年第6期2149-2158,共10页Chinese Journal of Geophysics

基　　金：中国科学院先导B计划(XDB41000000);国家自然科学基金(41674163,41574160,41704162,41974186,41904144);民用航天预研项目(D020308,D020104,D020303)资助.

摘　　要：地球外辐射带是一个高度动态变化的空间环境,辐射带电子通量的变化在磁暴期间尤为明显.要分析潜在的电子动态变化机制,需要排除绝热效应产生的影响.在以三个绝热不变量组成的相空间坐标中,利用相空间密度(PSD)可以反映电子的真实加速和损失情况.本文详细分析两颗范艾伦卫星和三颗GPS导航卫星在2013年3月的同步电子通量观测数据,发现在3月17日磁暴期间,当太阳风动压增大、行星际磁场南向时,辐射带电子通量会发生骤降.进一步将电子通量转换成电子相空间密度并利用不同第一、第二绝热不变量(μ,K)组合条件下PSD径向分布的差异性,深入探究磁暴期间辐射带电子的动态变化机制.结果表明:磁暴初期由于电子的局地加速导致PSD不断上升;磁暴主相期间,由于磁层顶阴影效应以及伴随的向外径向扩散损失导致PSD快速降低;位于不同空间位置的多颗卫星观测为明晰辐射带电子动态物理过程提供了重要的便利.The Earth′s outer radiation belt is highly dynamic,especially during geomagnetic storms.In order to uncover the underlying physics responsible for irreversible changes of radiation belt electrons,their variations in association with adiabatic effects need to be excluded.Calculations of electron phase space density(PSD)in the phase space coordinates in terms of the three adiabatic invariants are therefore important to investigate the real acceleration and loss processes of radiation belt electrons.By analyzing the electron flux data measured simultaneously by two Van Allen Probes and three GPS navigation satellites during the entire month of March2013,it is found that radiation belt electron flux dropouts occurred obviously during the 17 March geomagnetic storm in connection with southward IMF Bz and enhanced solar wind dynamic pressure.By investigating the electron PSD profiles and their differences for different pairs of the first and second adiabatic invariants,the non-adiabatic mechanisms attributed to the observed radiation belt electron variations are explored.It is indicated that during the initial phase of the geomagnetic storm electron PSDs increase due to the local acceleration processes,but electron PSDs drop quickly during the storm main phase mainly owing to the effect of magnetopause shadowing and associated outward radial diffusion.Overall,simultaneous measurements from multiple satellites with a broad spatial coverage facilitate in-depth understanding of radiation belt electron dynamic variations.

关 键 词：外辐射带 范艾伦卫星 GPS卫星 电子相空间密度 

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