New Results on the Polar Cap and PSBL Dynamics

A fundamental science goal of the International Solar Terrestrial Physics (ISTP) mission is to enhance understanding of how the solar wind couples its mass, momentum and energy into the magnetosphere. We present two new results from the UltraViolet Imager (UVI) and 3D Plasma experiments on spacecraft Polar and Wind that are relevant to this problem. First, we have found that the polar cap area which undergoes expansion and contraction can sometimes act independently of the interplanetary magnetic field (IMF). Second, we have discovered unidirectional ion beams in the plasma sheet boundary layer (PSBL) that propagate in the tailward direction immediately adjacent to the earthward propagating beam. Both of these observations are not predicted by current reconnection models. These new observations are indicating that other mechanisms may also be active.