吴晗^1,2,,
陈涛^1,,,
Kalegaev V. V.³,
Panasyuk M. I.³,
段素平¹,
何兆海¹,
李仁康⁴
1. 中国科学院国家空间科学中心, 空间天气学国家重点实验室, 北京 100190
2. 中国科学院大学, 北京 100049
3. 莫斯科罗蒙诺索夫国立大学, 核物理研究所, 俄罗斯 莫斯科 119234
4. 云南师范大学物理与电子信息学院, 昆明 650500

基金项目: 中国科学院战略性先导科技专项(XDA17010301，XDA17040505，XDA15052500，XDA15350201，XDA15016900)，国家自然科学基金项目(41874175，41931073)，国家重点实验室专项基金资助项目和中国科学院国家空间科学中心培育专项135项目(Y92111BA8S)以及云南省基础研究青年项目(2019FD111)资助


详细信息

作者简介: 吴晗, 女, 1992年生, 在读博士研究生, 从事辐射带中、高能电子通量对太阳风条件和地磁扰动的响应, 近地面大气电场与气象、人类活动、地震的关系等方面的研究.E-mail: hanwu92@qq.com

通讯作者: 陈涛, 男, 1961年生, 研究员, 从事空间物理与电磁探测、地球辐射带中波与带电粒子的相互作用、空间天气与全球变化的关系等方面的研究.E-mail: tchen@nssc.ac.cn

中图分类号: P353

收稿日期:2020-09-25
修回日期:2021-02-09
上线日期:2021-06-10

Statistical study of long-term dropouts of relativistic electron fluxes in the geosynchronous orbit

WU Han^1,2,,
CHEN Tao^1,,,
Kalegaev V. V.³,
Panasyuk M. I.³,
DUAN SuPing¹,
HE ZhaoHai¹,
LI RenKang⁴
1. State Key Laboratory of Space Weather, National Space Science Center, Chinese Academy of Sciences, Beijing 100190, China
2. University of Chinese Academy of Sciences, Beijing 100049, China
3. Skobeltsyn Institute of Nuclear Physics, Lomonosov Moscow State University, Moscow 119234, Russia
4. College of Physics and Electronic Information, Yunnan Normal University, Kunming 650500, China


More Information

Corresponding author: CHEN Tao,E-mail:tchen@nssc.ac.cn

MSC: P353

--> Received Date: 25 September 2020
Revised Date: 09 February 2021
Available Online: 10 June 2021


摘要
摘要:地球辐射带中有"杀手"电子之称的相对论电子通量增强和损失过程一直是空间物理学和空间天气学研究的热点.本文通过对2000—2016年间，地球同步轨道相对论电子通量降低至背景通量水平并持续时间长达3天以上这一特殊现象进行了相关统计研究.从事件的时间分布角度，本文研究了约1.5个太阳活动周内共62例事件随太阳活动水平高低的分布情况，结果表明：在太阳活动周下降期有较少的事件发生，而在峰年、谷年这类事件的发生率与太阳活动水平的高低并没有直接联系.随后，我们对这62例事件在开始、持续、结束三个阶段分别做了一些相关参数的统计，探讨相对论电子通量长期倒空事件的客观规律和产生机制.研究结果表明：事件发生前，太阳风动压、密度的显著增加引起磁层顶向内收缩，等离子体层顶一直维持在高L区域，IMF B_z分量南向和磁暴过程使相对论电子通量通过绝热和非绝热等物理损失机制降至背景通量水平.当这些相对论电子达到背景通量水平后，较弱的太阳风条件和地磁活动水平不足以提供充分的可以使相对论电子通量增长的源；虽然有些相对论电子通量长期倒空事件期间存在中、小磁暴过程，但这些强度较弱的磁暴很可能不会显著地影响同步轨道相对论电子损失和增长的动态平衡，因此相对论电子仍然可以维持在背景通量水平.如果有长时间的亚暴活动和高强度的ULF (Ultra-Low Frequency)波活动发生，太阳风速度显著增加，那么这些物理过程能提供足够的种子电子和持续的加速条件，使得相对论电子通量打破倒空状态，进而呈现显著增长趋势.
关键词: 地球同步轨道/
相对论电子/
长期倒空事件/
统计分析

Abstract:The enhancement and loss mechanisms of relativistic electron (known as killer electron) fluxes in the radiation belt have always been hotspots in the research area of space physics and space weather. In this paper, we study a special phenomenon that the relativistic electron flux in the geosynchronous orbit decreased to the background level and lasted for more than 3 days from 2000 to 2016. Firstly, we study the distribution of total 62 events in about 1.5 solar cycles with the sunspot number, the results show that fewer events occurred during the declining phase of a solar cycle. However, in the solar maximum and minimum, the occurrence of events did not seem to be directly related to the sunspot number. Then, in order to analyze and discuss the objective law and generation mechanism of the long-term dropouts of relativistic electrons, a statistical analysis on the beginning, continuation, and end periods of these 62 events is performed. The results show that before the event, the significant increase in solar wind dynamic pressure and density resulting in the inward movement of magnetopause, the maintenance of plasmapause at high L-shell for a long time, the southward IMF B_z component and the magnetic storm process reduced the relativistic electron flux to the background level through adiabatic and non-adiabatic physical mechanisms. When the relativistic electron reached the background flux level, weaker solar wind conditions and geomagnetic activities cannot provide enough sources for relativistic electrons; although sometimes there were some geomagnetic storms, they were small or medium geomagnetic storms. Under these circumstances, the physical mechanisms that led to the flux loss or enhancement during geomagnetic storms could keep a dynamic balance, so the relativistic electron still kept at background level. If long-term substorm activities, high-intensity ULF (Ultra-Low Frequency) wave activities or significant increase in solar wind occurred, these processes could provide enough seed electrons and acceleration mechanisms, so that the relativistic electron flux broke the dropout and presented a significant enhancement.
Key words:Geosynchronous orbit/
Relativistic electron/
Long-term dropout/
Statistical study



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