Research on the coupling process between the Magnetosphere-Ionosphere-Thermosphere by using HALL-MHD simulation predictions

为了理解磁层-电离层-热层之间的耦合过程，开发一个考虑所有耦合过程的模拟程序是至关重要的。本项目的一个目的是通过开发这样的模拟代码来更深入地了解耦合过程。我们以Kataoka[1999]编制的模拟程序为基础，尝试加入新的元素，如(1)热层中性风产生的发电机电场，(2)电子密度较低时出现的场向电场，(3)弯曲磁场的影响，(4)动能Alfven波精细结构的影响。GEOTAIL在磁层顶(MP)发现了一些关于这一点的实验证据。我们非常希望通过集群数据检查和查看是否真的存在霍尔…通过观察异相磁场，使重接线附近的电流更大。星系团由四颗相同的子卫星组成，它们一起飞行。它们每一个都有磁场和电场。船上的粒子和等离子体波仪器。当将我们的数据与发表的模拟的预期进行比较时，存在一些困难，例如：(1)MP上存在密度梯度，但到目前为止，所有的模拟都是在均匀的背景下进行的。密度梯度一定会降低事物的对称性。例如，人们预计霍尔电流在哪一侧更强，磁鞘或磁层侧？(2)当4颗卫星飞行通过特定的重连情况时，应该看到什么？为了了解发生在MP周围的无碰撞重连过程，第一步，我们尝试研究一个简单的重接场景，我们以前应用于与极光弧有关的磁层-电离层耦合过程的2-D Hall-MHD程序，但在本研究中，我们将离子-中性碰撞频率设置为零，并考虑了气压梯度项，并相应地修改了边界条件和背景参数。到目前为止，我们的模拟代码可以很好地处理MP场景，就像用GEOTAIL和CLUSTER等卫星观察到的那样。较少

In order to understand the coupling process between the magnetosphere-ionosphere-thermosphere, it is of vital importance to develop a simulation code which considers all coupling processes. An aim of this project is to understand the coupling process more deeply by developing such a simulation code. We were based on the simulation code made by Kataoka [1999], and made an attempt to include new elements such as (1)dynamo electric field originated by thermospheric neutral wind,(2)the field-aligned electric field which appears when the electron density is low,(3)a effect of bending magnetic field,(4)an effect of fine structures of kinetic Alfven waves.It has been suggested that the Hall term is important in collisionless reconnection and Hall-MHD might be a better basis in simulations and for theory than resistive MHD. Some experimental evidence for this has been found at the magnetopause (MP) from GEOTAIL. It is our great wish to check and see with CLUSTER data if there is really a Hall … More current close to the reconnection line by looking at the out-of-phase magnetic field. CLUSTER consists of four identical subsatellites and they fly together. Each of them has magnetic and electric fields. Particles and plasma wave instruments onboard. When comparing our data with expectations that come from the published simulations there are a few difficulties, for example:(1)there is a density gradient across the MP, but all simulations have been so far done with a homogeneous background. The density gradient must make things less symmetric. For example, on which side would one expect the stronger Hall current, the magnetosheath or magnetosphere side?(2)What should 4 satellites see when flying through a specific reconnection scenario?For the first step to understand the collisionless reconnection process occurring around MP, we try to study a simple reconnection scenario with the 2-D Hall-MHD code that we previously applied to a magnetosphere-ionosphere coupling process associated with an auroral arc but in the present study we set the ion-neutral collision frequency to zero and take into consideration of pressure gradient terms, and modify the boundary conditions and background parameters accordingly. So far, our simulation code can address the MP scenarios rather well as observed with satellites such as GEOTAIL and CLUSTER. Less