High‐lattitude convection patterns for various large‐scale field‐aligned current configurations

The large‐scale field‐aligned current system for persistent northward interplanetary magnetic field (IMF) is typically different from that for persistent southward IMF. One characteristic difference is that for northward IMF there is often a large‐scale field‐aligned current system poleward of the main auroral oval. This current system (the NBZ current) typically occupies a large fraction of the region poleward of the region 1 and 2 currents. The present paper models the high‐latitude convection as a function of the large‐scale field‐aligned currents. In particular, a possible evolution of the convection pattern as the current system changes from a typical configuration for southward IMF to a configuration representing northward IMF (or vice versa) is presented. Depending on additional assumptions, for example about the y‐component of the IMF, the convection pattern could either turn directly from a two‐cell type to a four‐cell type, or a three‐cell type pattern could show up as an intermediate state. An interesting although rather surprising result of this study is that different ways of balancing the NBZ currents has a minor influence on the large‐scale convection pattern.