Polar Cap Energy Deposition Events During the 5–6 August 2011 Magnetic Storm

Abstract

We study the 5–6 August 2011 storm for its energy deposition events occurring deep in the polar cap region, where the consequential localized intensifications of earthward directed Poynting flux led to the development of their related localized neutral density increases. For unraveling the underlying physical processes, we investigate the relations among Poynting flux intensifications, flow channels (FCs), and localized neutral density enhancements plus the nature of the underlying reconnection events. Observational results demonstrate Poynting flux increase deep in the polar cap in a FC‐2 type FC during magnetopause reconnections and in a FC‐4 type FC during lobe reconnections. During the latter stages of these different types of reconnection events, energy/momentum transfer occurred along old‐open field lines and commonly led to the development of localized neutral density increases during their respective upwelling events fueled by field‐aligned currents and above/within these polar FCs. The prevailing BY domination and the pulsed nature of this storm created favorable conditions for the development of these FC‐2 and FC‐4 types in the sunlit northern summer hemisphere and caused the observed Poynting flux intensifications deep in the polar cap. The solar wind source of these reconnections taking place along old‐open field lines was situated in the high‐latitude boundary layer. Thus, the high‐latitude boundary layer dynamo provided a vigorous source of energy/momentum transfer during the latter‐stage reconnections unfolding along old‐open field lines.