Preservation and variation of ion-to-electron temperature ratio in the plasma sheet in geo-magnetotail  

作　　者：ChuXin Chen 

机构地区：[1]Chinese Academy of Sciences Key Laboratory of Geospace Environment,Department of Geophysics and Planetary Sciences,School of Earth and Space Sciences,University of Science and Technology of China,Hefei 230026,China

出　　处：《Earth and Planetary Physics》2021年第4期337-347,共11页地球与行星物理（英文版）

摘　　要：The ion-to-electron temperature ratio is a good indicator of the processes involved in solar wind plasma entering and being transported inside Earth’s plasma sheet.In this study,we have demonstrated that patchy magnetic reconnection has the potential to preserve the ion-to-electron temperature ratio under certain conditions.If the charged particles are non-adiabatically accelerated no more than once in a single reconnection,the temperature ratio would be preserved;on the other hand,this ratio would not be preserved if they are accelerated multiple times.Consequently,under a northward interplanetary magnetic field(IMF)condition,the reconnection in the nonlinear phase of the Kelvin-Helmholtz instability is the dominant process for solar-originated plasma entering the Earth’s magnetosphere,and the ion-to-electron temperature ratio is preserved inside the plasma sheet.When the direction of the IMF is southward,the reflection of electrons from the magnetic mirror point,and subsequent multiple non-adiabatic accelerations at the reconnection site,are the primary reasons for the observed low ion-to-electron temperature ratio close to the Earth at midnight.While reconnections that occur in the night-side far tail might preserve the ratio,turbulence on the boundaries of the bursty bulk flows(BBFs)could change the ratio in the far tail through the violation of the frozen-in condition of the ions.The plateau in the contour of the calculated ion-to-electron temperature ratio in the down tail distance between 40 and 60 Earth radii may explain the strong correlation between the ion and electron temperatures in the outer central plasma sheet,which has not been clearly understood till date.

关 键 词：plasma sheet ion-to-electron temperature ratio patchy magnetic reconnection non-adiabatic acceleration bursty bulk flows far tail 

分 类 号：P354[天文地球—空间物理学]