磁尾的平衡结构

考虑到等离子体片和等离子体幔的存在,我们从Vlasov方程出发得出一个自洽的二维磁尾平衡模式。在这个模式中,假设等离子体处于平衡状态,压强是各向同性的,还假设沿磁尾方向各种参数的变化率较垂直于等离子体片方向的变化率要小得多。晨昏方向的变化则完全忽略不计。这个模式体现出磁尾的一些主要结构要素:(ⅰ)高温等离子体组成的等离子片;(ⅱ)等离子体片中的闭合磁力线;(ⅲ)等离子体极其稀薄的磁尾瓣;(ⅳ)等离子体幔;(ⅴ)磁层顶;(ⅵ)张开的磁尾。讨论了等离子体幔的存在对磁尾平衡结构的影响,结论是等离子体幔的存在使磁尾的形状更趋于尾形,于是,至少部分克服了Birn模式的困难。

THE STRUCTURE OF A EQUILIBRIUM MAGNETOTAIL

Considering the presence of the plasma sheet and the plasma mantle,we obtain a two-dimensional self-consistent equilibrium model of the magnetoteil based on the Vlasov equation.The model is characterized by an equilibrium state.The pressure is assumed to be isotropic.The gradients parallel to the tail are assumed to be much smaller than the perpendicular one.Our model is of two-dimensions,the gradients in y-direction are neglected.Our model includes a number of dominant structural elements: (1) the plasma sheet,a region of hot plasma; (2) the closed field lines inside the plasma sheet; (3) the tail lobe,regions of dilute plasma between plasma sheet and magnetopause; (4) the plasma mantle,regions of magnetosheath-like plasma inside and adjacent to the magnetopause; (5) magnetopause,the boundary of the magnetosphere; (6) the flaring magnetotail.We have discussed the influence of the presence of the plasma mantle on the equilibrium model of the magnetotail.The model tells that the presence of the plasma mantle makes the magnetotail more "tail" like.So it overcomes partly,at least,the difficulty in Birn's model.