高速流减速区特征研究:Hall MHD模拟

A study on property of high-speed flow-braking region:Hall MHD simulation

为了更深入理解磁层亚暴触发的物理机制,理论分析了近年来观测到的磁层亚暴过程中在近地磁尾出现的高速流减速区;采用数值模拟方法,分析了高速流减速区中的电磁力和压强梯度力,以及它们的合力在地向和尾向的相互作用。结果表明:携带磁结构的高速流地向运动,会造成近地磁通量和等离子体的堆积,形成减速区,开始时电磁力和压强梯度力的作用效果相当,而后,电磁力逐渐占主导地位,由于近地磁压和热压的增加,尾向力在减速区占主导地位,磁通量堆积区开始转为尾向运动,高速流退出减速区。

To understand the trigger mechanism of the magnetosphere substorm,the high-speed flow-braking region in the near-Earth magnetotail during subtorms observed in recently is analyzed theoretically.The electromagnetic and the pressure gradient force in the high-speed flow-braking region are studied by numerical simulating methods.The interaction of the composition of forces in earthward and tailward is analyzed in the region.Results show that the magnetic flux and plasma piles up because of the earthward moving high-speed flow with the magnetic structure,and then the high-speed flow-braking region comes into being. The electromagnetic and the pressure gradient force can be compared at beginning.The electromagnetic force becomes dominant slowly.With the increase of the magnetic and thermal pressure in the near-Earth,the earthward force dominates in flow-braking region.The region of the magnetic pileup moves tailward,and the high-speed flow withdraws from the braking region.