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Massive plasma transport across the magnetospheric low-latitude boundary layer

穿过磁层低纬度边界层的大量等离子体传输

基本信息

批准号：
13640446
负责人：
FUJIMOTO Masaki
金额：
$ 2.24万
依托单位：
Tokyo Institute of Technology
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
2001
资助国家：
日本
起止时间：
2001 至 2002
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-13640446/
关键词：
Eddy turbulence Magnetospheric low-latitude boundary layer Velocity shear layer Kelvin-Helmholtz instability Two-fluid simulation Finite electron inertia effects

项目摘要

This study aims at clarifying massive plasma transport across the magnetospheric low-latitude boundary layer, which would constitute a plasma sheet formation process that is totally different from the well-known. The new transport process at low-latitude is not expected in a pure MHD model and thus would involve coupling of dynamics over decades in temporal as well as spatial scales, from MHD down to the electron scales. In order to study the transport process that results from cross-scale coupling effects, we have performed numerical simulations of MHD phenomena using two-dimensional two-fluid simulation code including finite electron inertia effects.To be specific, we have simulated a development of MHD scale vortices that grow in velocity shear layers and have studied how the coupling to the electron dynamics emrges inside the MHD scale vortex.(1) When the flow is perpendicular to the magnetic field, the vortex roll-up motion produces an intese current layer, inside of which excited is an instability due to finite electron inertia. This produces a seeding perturbation for the secondary velocity shear instability at the outer edge of the vortex, which produces smaller vortices that destroy the parent vortex.(2) When there is an in-plane magnetic component, the field lines stretched by the roll-up motion are seen to reconnect. More dynamic reconnection is observed when the vortex size is larger relative to the electron scale.In either case, coupling to electron scales are observed within highly rolled-up MHD-scale vortices and this produces new effects not obtainable within the MHD framework. It is expected that these effects would lead to massive transport across the velocity shear layer.

这项研究的目的是阐明穿越磁层低纬边界层的大量等离子体传输，这将构成一个与众所周知的完全不同的等离子体片形成过程。新的低纬输送过程在纯MHD模式中是不被预期的，因此将涉及从MHD到电子尺度的时间和空间尺度上数十年的动力学耦合。为了研究由跨尺度耦合效应引起的输运过程，我们使用包含有限电子惯性效应的二维双流体模拟程序对MHD现象进行了数值模拟。具体地说，我们模拟了在速度剪切层中生长的MHD尺度涡旋的发展，并研究了这种耦合是如何在MHD尺度涡旋内部发生的。(1)当流动垂直于磁场时，涡旋卷起运动产生一个大电流层，在这个电流层内被激发的是由于有限电子惯性而引起的不稳定。这在涡旋外缘产生了二次速度剪切不稳定性的播种扰动，从而产生了较小的涡旋，破坏了母涡。(2)当存在面内磁场分量时，由于卷曲运动而拉伸的场线可以看到重新连接。当涡旋尺寸相对于电子尺度较大时，可以观察到更多的动态重联。在任何一种情况下，在高度卷曲的MHD尺度涡旋中观察到与电子尺度的耦合，这产生了在MHD框架内不能获得的新效应。预计这些影响将导致横跨速度剪切层的大量输送。