Theta aurora simulations: a new look at polar cap and magnetotail dynamics during periods of northward IMF Bz

Solar wind - magnetosphere coupling during periods of northward IMF Bz remains poorly understood; magnetospheric reconnection is minimized, and the open polar cap can all but disappear. The large scale (cross-polar) theta aurora is a phenomenon associated with northward IMF Bz in which a distinct auroral arc appears across the polar cap, connecting to both the dayside and nightside auroral oval. The theta aurora indicates a complex system of solar wind energy transfer into the magnetosphere, contrary to the expectation of low magnetospheric activity under northward IMF Bz conditions. We simulate multiple theta aurora events with the Space Weather Modeling Framework to investigate the polar cap and magnetotail dynamics during the theta aurora process. We find that the theta aurora is associated with intricate magnetic topologies within a highly twisted magnetotail as well as multiple reconnection regions along the magnetotail flank. Our high-resolution simulations also reveal the complete bifurcation of the polar cap during the theta aurora. Our findings connect the theta aurora to dynamic magnetospheric activity and further underscore the complexity of polar cap and magnetotail configurations during periods of northward IMF Bz.