NSWP: Formation and Characteristics of the Harang Reversal and Relations to Substorms: Simulations with the Rice Convection Model

众所周知，在被称为哈朗不连续面的区域中，电离层电场方向的反转在电离层和磁层的大范围动力学中发挥着重要作用。本项目使用赖斯对流模式(RCM)模拟哈朗逆转，以评估其形成和特征的物理过程，以及在亚暴期间的演变。RCM可以适当地考虑等离子体漂移在等离子体片内输运的物理过程，并通过场向电流的耦合自洽地求解电离层电势和等离子体片动力学。该项目将进一步开发更逼真的模拟。磁场解算器将提供与RCM等离子体压力保持力平衡的磁场。粒子边界条件将利用来自GeoTail卫星的观测建立。这个组合模型将被用来提供对据信支配哈朗逆转的物理过程的定量评估。模拟的定量结果将与地面雷达观测结果进行比较。为了评估潜在的物理过程，模型中的各个物理参数将发生变化，以了解这些变化如何影响Harang逆转。通过改变单个参数，同时保持其他参数不变，将有可能确定每个参数对Harang反转的形成和特征的影响。为了了解哈朗反转和磁亚暴之间的关系并检验亚暴理论，该项目将评估哈朗反转的演变及其与亚暴增长阶段和等离子体对流强减少后的初始阶段的相互关系。该项目将研究对流电场的减少是否会像理论预测的那样导致越来越快的变化和不稳定。这些模拟将首次提供对Harang逆转的定量评估，它与等离子体片的相关性，它在亚暴期间的演变和对行星际条件变化的反应，以及它对预测亚暴的潜在用途，这将是理解等离子体片内的磁层-电离层耦合和亚暴触发的关键。

The reversal in the direction of the ionospheric electric field in the region known as the Harang discontinuity is known to play an important role in the large-scale dynamics of the ionosphere and magnetosphere. This project uses the Rice Convection Model (RCM) to simulate the Harang reversal in order to evaluate the physical processes responsible for its formation and characteristics, as well as its evolution during substorms. The RCM can appropriately take into account the physics of the plasma drift transport within the plasma sheet, and it solves for the ionospheric electric potential self-consistently with the plasma sheet dynamics through their coupling by field-aligned currents. This project will further develop simulations to be more realistic. A magnetic field solver will provide magnetic fields that are in force balance with the RCM plasma pressures. Particle boundary conditions will be established using observations from the Geotail satellite. This combined model will be used to provide quantitative evaluation of the physical processes believed to govern the Harang reversal. The quantitative results from the simulations will be compared with ground-based radar observations. To evaluate the underlying physical processes, individual physical parameters in the model will be varied to see how the variations effect the Harang reversal. By varying a single paramter while keeping others fixed it will be possible to determine the effect of each parameter on the formation and characteristics of the Harang reversal. To understand the relationship between the Harang reversal and magnetic substorms and to test a substorm theory, this project will evaluate the evolution of the Harang reversal and its correlations to the plasma sheet during the substorm growth phase and during the initial stage after a strong decrease in plasma sheet convection. The project will examine whether or not a decrease in the convective electric field leads towards increasingly rapid changes and instability as predicted by the theory. The simulations will be the first to provide quantitative assessment of the Harang reversal, its correlations with the plasma sheet, its evolution and response to variations of interplanetary conditions during substorms, and its potential use to predict substorms, which will be crucial to understanding magnetosphere-ionosphere coupling within the plasma sheet and substorm triggering.