Numerical study on plasma dynamics in the Earth magnetosphere in association with characteristic distributions of aurora and field-aligned currents

到目前为止，地球磁层的理论模型通常假定动能为1-10keV的极光粒子在极光带上的通量管含量是均匀分布的。这意味着，尽管极光活动显著，但该区域没有发生电荷分离，而粘性相互作用和磁重联等边界过程在极光活动和区域1场向电流(FAC)的产生中发挥着重要作用。我们提出了一个新的悖论，即在一个向南的行星际磁场(IMF)期间，由于粒子沿开放场线逃逸，可以在极光椭圆上形成具有等离子体浓度的所谓等离子体‘环面’，而双胞对流对环面构型的扭曲导致了区域1和区域2的FAC的产生。等离子体环被假定为绝对交换不稳定的，因此它不被认为是磁层等离子体的真实分布。然而，如果考虑到跨开闭边界的磁漂移方向的反转，人们可以预期环面的整体构型可以保持不变，而交换不稳定性在环面内部局部发生。我们的理论预测，各种现象，如0区、1区和2区FAC的产生，以及离散极光和欧米伽带结构的形成，都被解释为等离子体环的活跃行为的结果，等离子体环通过等离子体流进入从太阳风到等离子体逃逸的旅行团的过程而被“新陈代谢”。我们数值模拟的目的是再现新陈代谢的环面以及极光现象。最近我们对0、1和2区的FAC和极光omega带的形成进行了模拟，模拟结果与卫星观测结果一致。

So far, the theoretical models for the earth magnetosphere have normally assumed that the distribution of auroral particles with kinetic energies of 1-10 keV is uniform, in terms of the flux tube content, over the auroralzone. This implies that no charge separation occurs in that region, despite of the remarkable activity of aurora, and that boundary processes such as viscous interaction and magnetic reconnection play important roles in the auroral activity and production of region 1 field-aligned currents (FACs). We propose a new paradogm that during a period of southward interplanetary magnetic field (IMF), the so-called plasma 'torus' with plasma concentration on the auroral oval can be formed due to particle escape along the open field lines, and that distortion of the torus configuration by the two-cell convection results in the generaation of the region 1 and region 2 FACs. The plasma torus had been assumed to be absolutely interchange-unstable, and thus it had not been considered as a realistic distribution of the magnetospheric plasma. However, if reversal of the magnetic drift direction across the open-close boundary is taken into account, one can expect that the whole configuration of the torus can be maintained while the interchange instability occurs locally inside it. Our theory predicts that various phenomena such as production of region 0,1 and 2 FACs and formations of discrete aurora and omega band structure are interpreted as results of active behavior of the plasma torus which is "metabolized" through the processes of plasma flow into the tours from the solar wind the plasma escape. The purpose of our numerical simulation is to reproduce the metabolized torus as well as those auroral phenomena. Recently we have obtained the simulation results of the region 0,1 and 2 FACs and the formation of auroral omega band, which are consistent with the satellite servations.