Statistics on the Magnetosheath Properties Related to Magnetopause Magnetic Reconnection
Statistics on the Magnetosheath Properties Related to Magnetopause Magnetic Reconnection
复制标题
与磁顶磁重联相关的磁鞘特性统计
DOI：
10.3847/1538-4357/ab290e
复制
发表时间：
2019
影响因子：
4.9
通讯作者：
Liu Libo
中科院分区：
文献类型：
--
作者：
Zhang Hui;Fu Suiyan;Pu Zuyin;Lu Jianyong;Zhong Jun;Zhu Changbo;Wan Weixing;Liu Libo
研究了磁鞘的性质，特别是与磁层顶磁重联(MR)有关的性质。(1)磁鞘中等离子体和磁场参数的分布存在不对称性。这些不对称性与行星际磁场(IMF)取向有关，它们要么是在弓形激波上产生的，要么是在磁鞘内部产生的。因此，在直接使用上游太阳风和IMF性质作为磁层顶MR启动条件时必须非常谨慎，因为磁鞘参数在每个地方都不相同。(2)在低纬和高纬磁层顶上，引入了一种独特的方法来估算通过磁流变穿过磁层的IMF磁通量。磁通量主要随三个独立的参数变化：国际货币基金组织钟角θCL、磁鞘等离子体β和太阳风声马赫数MS。令人惊讶的是，在向南和向北的国际货币基金组织条件下，通过磁层的磁通量是相似的。(3)磁层内部的磁偶极子倾角也控制着磁鞘参数。随着地球偶极子倾角的变化，等离子体压力脊的位置发生了变化，但仍保持在磁赤道附近。然而，无论偶极子倾角有多大，磁层顶上磁鞘流动的停滞点都保持在太阳下点。这些行为可以决定MR的位置和磁层顶上通量转移事件的产生。
Magnetosheath properties, particularly those related to magnetopause magnetic reconnection (MR), are investigated in this study. (1) Asymmetries are found to exist in the distributions of plasma and magnetic field parameters in the magnetosheath. These asymmetries are related to the interplanetary magnetic field (IMF) orientation, and they are produced either on the bow shock or inside the magnetosheath. Thus, one must be very cautious in directly using the upstream solar wind and IMF properties as the magnetopause MR initiation conditions, since the magnetosheath parameters are not the same everywhere. (2) A unique method is introduced to estimate how much IMF magnetic flux passes through the magnetosphere via MR on either the low-latitude or the high-latitude magnetopause. This flux mainly varies with three independent parameters: the IMF clock angle θCL, the magnetosheath plasma β, and the solar wind sound Mach number MS. Surprisingly, the magnetic fluxes passing through the magnetosphere are comparable under the southward and northward IMF conditions. (3) The dipole tilt angle, the property from the inside of the magnetosphere, also controls the magnetosheath parameters. As the Earth’s dipole tilt angle varies, the plasma pressure ridge shifts its location but remains near the magnetic equator. The stagnation point of the magnetosheath flow on the magnetopause, however, remains at the subsolar point no matter how large the dipole tilt angle is. These behaviors may be determinative of the locations of MR and the generation of flux transfer events on the magnetopause.