• ISSN 2097-1893
  • CN 10-1855/P

太阳高能电子事件

王雯 王玲华

引用本文: 王雯,王玲华. 2022. 太阳高能电子事件. 地球与行星物理论评(中英文),53(0):1-13
Wang W, Wang L H. 2022. Solar energetic electrons events. Reviews of Geophysics and Planetary Physics, 53(0): 1-13 (in Chinese)

太阳高能电子事件

doi: 10.19975/j.dqyxx.2022-040
基金项目: 国家自然科学基金资助项目(42127803,42150105);民用航天“十三五”技术预先研究日球层边际探测重要科学问题资助项目(D020301)
详细信息
    作者简介:

    王雯(1994-),男,博士研究生,主要从事太阳高能电子的研究. E-mail:wenwang@pku.edu.cn

    通讯作者:

    王玲华(1977-),女,教授,主要从事日球层高能粒子物理的研究和仪器研制. E-mail:wanglhwang@pku.edu.cn

  • 中图分类号: P353.8

Solar energetic electrons events

Funds: Supported by the National Natural Science Foundation of China (Grant Nos. 42127803, 42150105), and the "13th Five-Year Plan" Technology Advance Research Funding Project for Important Scientific Issues in Heliospheric Marginal Exploration (Grant No. D020301)
  • 摘要: 太阳高能粒子事件是行星际中观测到的最常见的太阳粒子加速现象之一. 太阳高能粒子事件根据主导粒子的不同可以分为质子主导的大太阳高能粒子事件和电子主导的富含3He/电子太阳高能粒子事件. 其主要区分为大太阳高能粒子事件中,3He/4He~5×10-4比率与日冕相同,而电子主导的富含3He/电子太阳高能粒子事件,3He/4He>0.01,远高于日冕. 太阳高能电子事件在太阳上的释放时间可以分为低能(~10 keV以下)电子和高能(~15 keV以上)电子两组,高能电子相较于低能电子延迟释放~20 min,对应此时日冕物质抛射高度距日心约2个太阳半径,而与之相关的富含3He离子的释放相较于电子释放延迟1小时左右,对应此时日冕物质抛射高度距日心约5.7个太阳半径. 太阳高能电子事件的能谱一般呈现为双幂律谱形式,低能谱指数1.9±0.3和高能谱指数3.6±0.7,弯折能量~60 keV,低能谱指数与高能谱指数呈现明显正相关,而低能高能谱指数与弯折能量没有明显相关;也有部分事件呈现单幂律谱的形式,谱指数为3.5±1.2. 前人统计研究发现,约有~45%的15 keV以上有观测的太阳高能电子事件与硬X射线耀斑相关,通过比较50 keV以上,太阳高能电子事件能谱以及相关联X射线耀斑的能谱发现,这些事件中的高能硬X射线谱指数与电子事件高能能谱指数呈现正相关,但与经典韧致辐射理论预测不符合;并且通过对高能电子事件电子总数的估算发现,高能电子事件的电子总数仅为耀斑中产生硬X射线的电子总数的~0.1%~1%. 本文更进一步地研究了16个同时具有良好电子观测(能量覆盖5~200 keV)和硬X射线观测(能量覆盖3~80 keV)的电子事件,根据电子通过相对论厚靶韧致辐射机制产生X射线可以反推出产生硬X射线的电子能谱,通过对比电子能谱指数和产生硬X射线的电子谱指数发现,低能电子谱指数与产生硬X射线的电子谱指数呈现正相关,但所有事件低能电子谱指数明显小于产生硬X射线的电子谱指数;而电子事件的高能电子谱指数与产生硬X射线的电子谱指数的对比发现,半数事件中,电子高能谱指数与产生硬X射线的电子谱指数一致,而另一半事件中,产生硬X射线的电子谱指数陡于实地观测到的电子高能谱指数. 这16个事件也伴随强3He的观测,有13个是明显3He/4He>0.01的富含3He电子事件,另外3个3He/4He<0.01. 16个事件中有15个事件日冕仪的观测并且其中14伴随日冕物质抛射. 通过将考虑行星际传播过程中能量损失的模拟电子事件能谱与观测对比,可以知道电子事件的源区应该处于高日冕(~1.3太阳半径),考虑密度模型的变化之后,源区位置也处于高日冕(约1.1~1.3太阳半径),并且基于这些结果,本文提出新的太阳高能电子事件加速物理图像.

     

  • 图  1  水手4号观测到的~40 keV能量太阳高能电子的通量随时间变化(修改自Van Allen and Krimigis, 1965

    Figure  1.  Temporal profile of ~40 keV electrons from Sun, observed by Mariner 4 (modified from Van Allen and Krimigis, 1965)

    图  2  WIND卫星观测到的太阳高能电子的通量随时间变化. (a)脉冲型事件,通量随时间变化呈现快速上升快速下降特征. (b)渐变型事件,呈现快速上升慢速下降特征(修改自Wang et al., 2012

    Figure  2.  Temporal profile of solar energetic electron events, observed by WIND. (a) Impulsive event, characterized by a fast-rise, fast-decay temporal profile. (b) Gradual event, characterized by a fast-rise, slow-decay temporal profile (modified from Wang et al., 2012)

    图  3  在太阳上推测的电子事件释放时间(菱形)与III型射电暴(虚线)释放时间的比较(修改自Wang et al., 2006

    Figure  3.  Comparison of the start times of inferred electron injections at different energies (diamonds) and the release time of type III burst (dash line) at the Sun (modified from Wang et al., 2006)

    图  4  WIND/3DP观测的电子事件通量随时间变化(黑色曲线)以及利用正演模型得到的拟合的电子通量随时间变化(红色曲线). 虚线表示III射电暴(底图)的起始时间(引修改自Wang et al., 2006

    Figure  4.  Comparison between electron temporal profile observed by WIND/3DP (black curves) and fitted electron temporal profile at 1 AU (red curved). Dashed line indicates onset time of type III radio burst (bottom panel) (modified from Wang et al., 2006)

    图  5  (a)最佳拟合得到的电子(黑色)与离子(红色)在太阳上释放通量随时间变化,释放起始时间用圆圈表示,粒子速度单位为光速c. 虚线代表III型射电暴释放时间. (b)10个电子事件中离子、高能电子、相对与低能电子的释放延迟. (c)根据日冕物质抛射速度线性外推得到的日冕物质抛射在各粒子释放时间时处于的高度. 图(b)和图(c)中圆圈表示粒子释放起始时间,红色表示离子,蓝色表示高能电子,黑色表示低能电子(修改自Wang et al., 2016

    Figure  5.  (a) Best-fit temporal profile of electrons (black) and ions (red) at the Sun. Release time is marked with circles; Particle speed is normalized by light speed c. Dash line represents the release time of type III burst. (b) The time delay of ions and high energy electrons, relative to low energy electrons for the ten events. (c) The altitude of CMEs at the release time of particles, estimated by a constant CME speed times time delay. In figure (b) and (c), particle release times of ions (red), high energy electrons (blue) and low energy electrons (black) are marked by circles (modified from Wang et al., 2016)

    图  6  (a)WIND卫星所观测到的电子事件样例,其峰值电子微分通量随能量变化(星号表示WIND 静电分析仪的观测,加号表示半导体探测器的观测),黑色曲线表示背景通量. 蓝色和红色直线表示双幂律谱能谱中的低能段和高能段. (b)低能谱指数(蓝色)和高能谱指数(红色)的统计直方图. (c)弯折能量的统计直方图. (d)低能谱指数和高能谱指数的散点图. 红色直线是其线性拟合的结果. (e)低能谱指数(蓝色十字)和高能谱指数(红色十字)对弯折能量的散点图(修改自Krucker et al., 2009

    Figure  6.  (a) An example of solar energetic electron event observed by WIND spacecraft. The peak differential flux vs. energy are marked with stars (observed by WIND/3DP) and crosses (observed by WIND/SST). Black curves represent background detection. (b) Histograms of low energy spectral indexes (blue) and high energy spectral indexes (red). (c) Histograms of break energies. (d) The scatter diagram between low energy spectral indexes and high energy spectral indexes. The red line shows the linear regression. (e) The scatter diagram between break energy and low energy spectral indexes (blue) [high energy spectral indexes (red)] (modified from Krucker et al., 2009)

    图  7  (a)电子事件峰值能谱(顶部黑色十字)与硬X射线耀斑峰值能谱(底部黑色柱状线)的比较. 电子事件呈现双幂律谱,黑色直线和蓝色直线分布代表低能段和高能段能谱拟合. 黑色虚线表示背景. 硬X射线耀斑峰值能谱拟合由两部分组成:热麦氏拟合(红色曲线)和非热双幂律谱拟合(折线,黑色部分表示双幂律谱低能,蓝色表示双幂律谱高能). 黑色曲线表示背景. (b)50 keV以上,高能电子和硬X射线谱指数的散点图. 散点处的直线为线性拟合直线,虚线表示1:1关系. 散点周边的两条直线分别表示厚靶(THICK target)和薄靶(THIN target)韧致辐射模型给出的理论谱指数关系. (c)硬X射线耀斑中电子总数与逃逸电子总数的散点图,直线表示线性拟合结果,虚线表示1:1关系(修改自Krucker et al., 2007

    Figure  7.  (a) Comparison between solar energetic electron event peak spectrum (Top, black crosses) and hard X-ray flare peak spectrum (Bottom, black histogram). Top: Electron spectrum is fitted with double-power-law shape (black line indicates low energy part and blue line indicates high energy part). Dash line shows the background. Bottom: X-ray spectrum is fitted with a thermal component (red curve) plus a double-power-law nonthermal component (black line indicates low energy part and blue line indicates high energy part). Black curve indicates the background. (b) The scatter diagram of spectral indexes between electron events and X-ray flares at energies above 50 keV. Dash line shows 1:1 relation and black line shows the linear regression. The black lines show the theoretical relationship between electron spectral indexes and X-ray spectral indexes based on Thick target (Top) and Thin target (bottom) bremsstrahlung mechanism. (c) The scatter diagram between the total number of electrons in X-ray flares and the total number of escaping electrons. Black line represents the linear regression. Dash line shows 1:1 relation (modified from Krucker et al., 2007)

    图  8  (a)电子事件通量随时间变化. (b)电子事件峰值能谱(三角)和双幂律谱拟合(黑色折线). 虚线表示背景. (c)低能电子能谱谱指数与产生硬X射线的电子谱指数散点图,虚线表示1:1关系. (d)X射线耀斑通量随时间变化. (e)X射线耀斑峰值能谱(黑色柱状线)以及能谱拟合:热麦氏(红色曲线)加上双幂律谱(蓝色折线)拟合. 绿色直线表示厚靶韧致辐射模型得到的产生X射线电子的能谱. 黑色虚线为背景. (f)高能电子能谱谱指数与产生硬X射线的电子谱指数散点图,虚线表示1:1关系(修改自Wang et al., 2021

    Figure  8.  (a) Temporal profile of electron fluxes for the solar energetic electron event. (b) Peak energy spectrum (triangle) of the electron event, fittted with a double-power-law shape (black line). Dash line represents the background. (c) The scatter diagram between the low energy spectral indexes of electron events and the spectral indexes of hard X-ray producing (HPE) electrons. Dash line shows 1:1 relation. (d) Temporal profile of X-ray fluxes during the flare. (e) Peak energy spectrum (black histogram) of the X-ray flare, fittted with a thermal component (red curve) plus a nonthermal double-power-law (blue line). Dash line represents the background. Green line represents the spectrum of hard X-ray producing electrons derived through relativistic thick target bremsstrahlung mechanism. (f) The scatter diagram between the high energy spectral indexes of electron events and the spectral indexes of HPE electrons. Dash line shows 1:1 relation (modified from Wang et al., 2021)

    图  9  (a)3He/4He比与低能电子事件谱指数,(b)高能电子事件谱指数和(c)产生硬X射线的电子谱指数的散点图(修改自Wang et al., 2021

    Figure  9.  The scatter diagram between (a) 3He/4He and low energy electron spectral indexes, (b) high energy electron spectral indexes, and (c) the spectral indexes of hard X-ray producing electrons (modified from Wang et al., 2021)

    图  11  交换重联耀斑模型和新太阳高能电子事件加速物理图像的对比(修改自Wang et al., 2021

    Figure  11.  Interchange reconnection flare model and the schematic for the acceleration of solar energetic electron events (modified from Wang et al., 2021)

    图  10  在太阳源区处假设的电子事件的双幂律谱能谱,以及假设源区不同高度后(距日心1.02~2.0太阳半径),从源区到1 AU考虑传播过程中能量损失后的电子能谱(修改自Wang et al., 2021

    Figure  10.  Presumed double-power-law shape of energy spectrum for electron events at solar source region. The corresponding energy spectrum at 1 AU after considering energy losses during the transportation from the Sun to 1 AU, by assuming different altitudes (from a heliocentric distance of 1.02 solar radius to 2.0 solar radius) of the source region (modified from Wang et al., 2021)

    表  1  太阳高能粒子事件的分类特征

    Table  1.   Characteristics of solar energetic particle events

    特征大太阳高能粒子事件
    (渐变型太阳高能粒子事件)
    富含电子/3He的太阳高能粒子事件
    (脉冲型太阳高能粒子事件)
    主导粒子类型 能量约10 MeV以上的质子 约1~100 keV的电子
    电子质子比
    3He/4He丰度 日冕丰度 ~5×10−4 ~1
    持续时间 数天 数小时
    发生频率(太阳活动极大期) ~10/年 ~104/年
    与其他现象的相关
    耀斑 通常伴随大耀斑 约1/3伴随耀斑(通常为小耀斑)
    软X射线 渐变型(持续数小时) 脉冲型(持续数十分钟以内)
    日冕物质抛射(CME) 快速CME 日面西侧CME/喷流
    射电暴 II型射电暴 III型射电暴
    下载: 导出CSV
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出版历程
  • 收稿日期:  2022-04-27
  • 录用日期:  2022-06-16
  • 修回日期:  2022-06-15
  • 网络出版日期:  2022-06-18

目录

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    返回文章
    返回