Studies on Cowling channel usingglobal Magnetosphere-Ionosphere coupling simulator

我们通过剪切阿尔文波提出了电离层水平电流（包括霍尔电流）和场对准电流（FAC）之间耦合的第一个完整公式，它可以描述 Cowling 通道的形成，而无需二次（霍尔极化）电场强度的任何先验参数化。我们的理论将整流罩通道分为“主要”和“次要”部分。到目前为止，还没有理论框架可以单独从观察到的或给定的总电导、电场和 FAC 分布中导出这些分离的分量。但是，当将给定的入射阿尔文波视为驱动器时，反射波可以唯一地分解为初级分量和次级分量。我们证明，根据实际情况，反射波确实可以携带连接到发散霍尔电流的 FAC。通过这种新方法，我们可以确定产生多大的二次电场来关闭电离层内发散的霍尔电流，以及有多少霍尔电流继续以 FAC 的形式到达磁层。在典型的电离层情况下，只有一小部分 FAC 以电导梯度连接到霍尔电流，即二次场相对较强。但是，当电导与阿尔文电导相比相对较低和/或水平尺度小于 ~10 [km] 时，霍尔 FAC 可能会变得很重要。

We present the first complete formulation of the coupling between the ionospheric horizontal currents (including Hall currents) and the field-aligned currents (FAC) via shear Alfven wave, which can describe the formation of a Cowling channel without any a priori parameterization of the secondary (Hall-polarization) electric field strength. Our theory separates the Cowling channel into "primary" and "secondary" components. Until now there are no theoretical frameworks, which can derive these separated components from observed or given total conductance, electric field and FAC distributions alone. But when a given incident Alfven wave is considered as the driver, the reflected wave can be uniquely decomposed into the primary and secondary components. We show that the reflected wave can, depending on actual conditions, indeed carry FAC that connect to divergent Hall currents. With this new method wecan identify how large secondary electric field is generated to close the divergent Hall current withinthe ionosphere, and how much of the Hall current continues out to the magnetosphere as FAC. In typical ionospheric situations only a small fraction of FAC is connected to Hall currents at conductance gradients, i.e. the secondary field is relatively strong. But when conductances are relatively low compared with Alfven conductance and/or horizontal scales smaller than ~10 [km], the Hall FAC may become significant.