磁尾等离子片中偶极化锋面的数值模拟研究

利用守恒型TVD格式对8波模型磁流体方程组进行数值模拟, 对磁尾中偶极化锋面的物理和演化特性进行研究. 构建了由BBF类型通量管机制产生的偶极化锋面数值模拟模型, 该模型由磁尾平衡模型、亚暴增长相模型和亚暴触发及BBF形成模型三部分组成. 数值模拟结果很好地再现了磁尾中BBF类型通量管机制产生的偶极化锋面特性. 伴随着高速 流的出现, 磁场B_z分量呈非对称双极变化结构, 即锋面前减小为负值, 在锋面上急剧增大. 当B_z增大到极大值后回落并趋于稳定. 随着偶极化锋面伴随地向高速流向地球运动, 偶极化锋面上B_z的变化越来越小. 

Numerical Simulation of Dipolarization Fronts in the Plasma Sheet of Magnetotail

This paper focuses on the numerical simulation of the physical and evolution features of the Dipolarization Fronts (DFs) by using the eight-wave MHD equations based on the conservation TVD scheme. Firstly, a numerical model of DFs which is produced by BBF flux is built up. It is made up of three parts, i.e., magnetotail balance model, substorm growth phase model and substorm triggering BFF model. The result of numerical simulation presents the features of the DFs caused by BBF flux. With the appearance of high speed flow, magnetic field B_z component shows the changing asymmetric bipolar structure, which means that pre-front decreases to negative while expands rapidly on the DFs. When B_z increases to its maximum, it falls and becomes stable. With the DFs moving earthward while the high speed flow heading to the same direction, B_z on the DFs changes less and less. The generations of high speed flux and the DFs make a wider differentiation in the tail. Therefore, B_z component starts sinking, which can be explained as the plasma of the earthward compression of the DFs generated by the speed differentiation.