磁尾中交换不稳定性所产生偶极化锋面的动力学特性研究

本文利用考虑了Hall效应和有限Larmor半径（FLR）效应的磁流体数值模拟研究了在离子惯性长度/离子Larmor半径尺度内偶极化锋面的动力学特性.偶极化锋面由磁尾近地区域中由于热压尾向梯度和磁场曲率力不平衡所引起的交换不稳定性自洽产生.数值研究表明，偶极化锋面是切向间断，在相对该锋面结构静止的参考系中等离子体穿过偶极化锋面的法向速度为零.Hall效应主要影响与偶极化锋面的切平面相正交的电场，使得锋面切向电流增大，同时产生锋面结构不对称.研究表明离子在Larmor半径尺度产生的FLR效应可导致锋面结构的大尺度漂移运动.由FLR效应产生的离子磁化流速在偶极化锋面的日下点处指向昏向，锋面后区域的速度晨向分量增长，从而导致整个锋面结构向晨向漂移.

On the kinetic nature of dipolarization fronts produced by interchange instability in the magnetotail

A two-dimensional extended MHD simulation, including Hall effect and finite Larmor radius (FRL) effect, is performed to study the kinetic nature of dipolarization fronts (DFs) in the scale of the ion inertial length/ion Larmor radius. The DF is self-consistently produced by the interchange instability, arising due to the force imbalance between the tailward gradient of thermal pressure and Earthward magnetic curvature force in the near-Earth region. Numerical investigations indicate that the DF is a tangential discontinuity, which means that the normal plasma velocity across the DF should be zero in the reference system that is static with the DF structure. Hall effect arising in the scale of ion inertial length determines the electric system, including electric field and current. Hall effect mainly contributes on the electric field normal to the tangent plane of the DF, increases the current along the tangent plane of the DF, but also makes the DF structure asymmetric. The drifting motion of the large-scale DF structure is determined by the FLR effect arising in the scale of ion Larmor radius. The ion magnetization velocity induced by the FLR effect is towards to duskward at the subsolar point of the DF, but the dawnward component of velocity in the region after the DF is increased, which dominantly results in the drifting motion of the whole mushroom structure towards the dawn.