Studies on Cowling channel usingglobal Magnetosphere-Ionosphere coupling simulator

我们提出了电离层水平电流（包括霍尔电流）和场向电流（FAC）之间通过剪切Alfven波耦合的第一个完整公式，它可以描述Cowling通道的形成，而不需要任何先验的二次（霍尔极化）电场强度参数化。我们的理论将Cowling通道分为“初级”和“次级”两个部分。到目前为止，还没有理论框架可以从观察到的或给定的总电导、电场和FAC分布中推导出这些分离的成分。但当给定的入射阿尔芬波作为驱动时，反射波可以唯一地分解为一次分量和二次分量。我们表明，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，我们可以确定在电离层内产生多大的二次电场来关闭发散的霍尔电流，以及有多少霍尔电流以FAC的形式继续到磁层。在典型的电离层情况下，只有一小部分FAC在电导梯度下与霍尔电流相连，即二次场相对较强。但当电导与阿尔芬电导相比相对较低和/或水平尺度小于~10 [km]时，霍尔FAC可能变得显着。

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.