暴时等离子体层顶密度不规则结构对SAR弧的调制  

Modulation of a SAR arc by density irregularities at plasmapause during a geomagnetic storm

作　　者：向溢民 袁志刚[1] 薛祖祥 余雄东 黄政 XIANG YiMin;YUAN ZhiGang;XUE ZuXiang;YU XiongDong;HUANG Zheng(School of Electronic Information Wuhan University,Wuhan 430072,China)

机构地区：[1]武汉大学电子信息学院,武汉430072

出　　处：《地球物理学报》2023年第11期4413-4428,共16页Chinese Journal of Geophysics

基　　金：国家自然科学基金(41925018,41874194);国家重点研发计划(2022YFF0503700)资助。

摘　　要：SAR弧的磁层源区对应环电流与等离子体层顶重叠区域,而等离子体层顶常常观测到密度不规则结构.之前还没有暴时等离子体层顶密度不规则结构对SAR弧调制的观测报道.本文报道了地基成像和磁层、电离层卫星对2013年10月9日磁暴恢复相期间发生的SAR弧的联合观测事件.在SAR弧的磁层源区,Van Allen Probe B卫星观测到了密度不规则结构,其中存在EMIC波、环电流离子分布和非线性电场结构.联合观测表明:该区域中的环电流离子分布通过库伦碰撞产生的热流通量足以驱动SAR弧,热流通量受到密度不规则结构的调制,形成空间上的小尺度分布,环电流离子中几keV的质子和几十keV的氧离子对这个过程起主导作用;此外,位于等离子体层顶密度不规则结构的低密度区的非线性结构电场引起的低能电子沉降可能是造成这次SAR弧非常明亮的原因.The magnetospheric source region of the Stable Auroral Red(SAR)arc corresponds to the overlap of the ring current and the plasmapause.Although the density irregularities are often observed at the plasmapause,it has not been reported that the modulation of a SAR Arc by the density irregularities at plasmapause yet.This paper reports the conjugate observation of a SAR arc by ground-based imaging,magnetospheric and ionospheric satellites during the recovery phase of the geomagnetic storm on October 9,2013.In the magnetospheric source region of the SAR arc,the Van Allen Probe B satellite observes density irregularities,in which there are EMIC waves,ring current ion distribution,and nonlinear electric field structures.The conjugate observation shows that the distribution of ring current ions in this region is capable of driving the SAR arc through the heat flux generated by Coulomb collisions.The heat flux is modulated by density irregularities,forming small-scale spatial distributions.Both Protons with energies of several keV and oxygen ions with energies of tens of keV in the ring current play a dominant role in this process.Additionally,the precipitation of low-energy electrons caused by nonlinear electric field structures superimposed on the heat flux should be attributed to the very bright SAR arc.

关 键 词：SAR弧 密度不规则结构 库伦碰撞 非线性电场结构 等离子体层电子 环电流离子 

分 类 号：P351[天文地球—空间物理学]