基于范艾伦卫星观测数据的地球辐射带电子能谱分布的统计分析  

Statistical Analysis of Distributions of Electron Energy Spectra in the Earth’s Radiation Belts Based on Van Allen Probes Observations

作　　者：王建行 项正 马新 郭德宇 董俊虎 刘阳希子 胡景乐 倪彬彬[1] WANG Jianhang;XIANG Zheng;MA Xin;GUO Deyu;DONG Junhu;LIU Yangxizi;HU Jingle;NI Binbin(Department of Space Physics,Wuhan University,Wuhan 430072)

机构地区：[1]武汉大学空间物理系,武汉430072

出　　处：《空间科学学报》2024年第3期446-457,共12页Chinese Journal of Space Science

基　　金：国家自然科学基金项目(42025404,42188101,42174190);国家重点研发计划基金项目(2022 YFF0503700);中国科学院战略性先导科技专项(B类)(XDB41000000);民用航天技术预先研究项目(D020308,D020104)共同资助。

摘　　要：利用范艾伦卫星2014年至2018年观测的高精度电子能谱数据,统计分析了不同辐射带高能电子能谱类型的时空分布特征.结果表明,辐射带电子能谱主要被分为三类:指数分布能谱、幂律分布能谱和反转能谱.指数分布能谱通常在等离子体层以外占主导地位.幂律分布能谱通常在磁暴的主相出现在高L处,并逐渐转移到低L处.在地磁活动平静时期,幂律分布能谱在高L处存在时间更长,占比更多.反转能谱在等离子体层内L>2.5处占主导地位,随着等离子体层层顶升高,反转能谱增加,指数分布能谱减少.在长时间的地磁活动平静年份,辐射带电子反转能谱局地峰值(约2 MeV)附近的电子通量明显较低,反转能谱占比较少.辐射带电子能谱类型对等离子体层层顶和地磁活动依赖性的统计分析表明,反转能谱发生率的峰值位置约位于L=(L_(pp)–2)(L_(pp)为等离子体层层顶位置),指数分布能谱发生率的峰值约位于L=(L_(pp)+1.5),幂律分布能谱的出现与电子的注入密切相关.磁暴越剧烈,反转能谱被指数分布能谱取代的L范围越广泛.在平静时期,由于等离子体嘶声的散射作用,等离子体层层顶内的指数分布能谱被反转能谱取代.本文给出了辐射带电子能谱类型长期的时空分布特征,可以为辐射带动态建模和高能电子通量预报提供理论参考.The characteristics of energy spectra distributions of radiation belt electrons can help re-veal the dominant physical mechanism behind the dynamics of the radiation belt.In this study,the tem-poral and spatial distribution characteristics of energy spectra of energetic electrons are statistically ana-lyzed using the measurements from Van Allen probes during 2014–2018.The results show that most of the electron spectra in the radiation belt can be classified into three types:exponential,power-law and reversed spectra.The exponential spectra dominate in the outer radiation belt outside the plasmapause.The power-law spectra usually occur at higher L values and move to lower L values during geomagnetic storms.During quiet geomagnetic activity periods,the power-law energy spectra stay at the high L with longer time and higher proportion.The reversed energy spectra dominate at L>2.5 inside the plasmas-phere.As the increase of plasmapause locations,more reversed energy spectra occur while the propor-tion of the exponential energy spectra decreases.During long-term quiet periods,electron fluxes near the peak of the reversed energy spectra(about 2 MeV)are relatively low to form obvious reversed spectral.The results also show that the peak location of reversed energy spectra is about 2 L inside the plasma-pause while the peak location of exponential energy spectra is about 1.5 L outside the plasmapause.Ap-pearances of power-law energy spectra are related to substorm injections of electrons.Stronger magnetic storms produce wider L ranges where reversed energy spectra are replaced by exponential spectra.Dur-ing quiet times,exponential energy spectra inside the plasmapause are replaced by reversed energy spec-tra due to pitch angle scattering produced by plasmaspheric hiss waves.

关 键 词：辐射带 电子能谱 范艾伦探测器 地磁活动 等离子体层层顶 

分 类 号：P353[天文地球—空间物理学]