Abstract

A thin current sheet in the Earth’s magnetotail with characteristic thickness of one to several proton gyroradii is often observed during magnetospheric disturbances named substorms, when a relatively thick current configuration in the magnetotail is narrowed to an extremely small thickness and then can spontaneously be destroyed. The current-sheet destruction is usually accompanied by such active processes as plasma acceleration and heating, as well as generation of an induced electric field and magnetohydrodynamic waves. In this paper, we developed and investigated a model of formation of a thin current sheet in which, along with protons, we have taken into account single-charged oxygen ions coming from the ionosphere into the magnetotail current sheet during magnetically active periods. The aim of this simulation is to study the peculiarities of thin current-sheet formation in two-component plasma and investigate its structure. It is shown that equilibrium configuration can have some characteristic properties. In particular, if the system consists only of protons or heavy ions, single-scale current equilibrium supported by quasi-adiabatic particles is formed. When a current sheet is formed in plasma that consists of a mixture of protons and oxygen ions in comparable concentrations, a current sheet can be formed with heavy ions as current carriers and chaotic proton trajectories that make a negative contribution to the current, due to which the current-density profile becomes bifurcated with the minimum at the center and maxima at the periphery of the sheet. The results may be useful for the interpretation of observational data in the Earth’s magnetotail.

中文翻译：

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氧离子对磁尾中薄电流片形成的影响

摘要

在称为亚暴的磁层扰动期间，经常观察到地球磁尾中具有一到几个质子陀螺半径特征厚度的薄电流片，当磁尾中相对较厚的电流配置变窄到极小的厚度，然后可以自发地被破坏。电流片破坏通常伴随着等离子体加速和加热等活跃过程，以及感应电场和磁流体动力波的产生。在本文中，我们开发并研究了薄电流片的形成模型，其中与质子一起，我们考虑了在磁活动期间从电离层进入磁尾电流片的单电荷氧离子。该模拟的目的是研究双组分等离子体中薄电流片形成的特性并研究其结构。结果表明，平衡配置可以具有一些特征。特别地，如果系统仅由质子或重离子组成，则形成由准绝热粒子支持的单尺度电流平衡。当在由相当浓度的质子和氧离子混合物组成的等离子体中形成电流片时，可以形成以重离子作为载流子和对电流产生负贡献的混沌质子轨迹的电流片，由于电流密度分布变得分叉，最小值在中心，最大值在片材的外围。