Limited impact of escaping photoelectrons on the terrestrial polar wind flux in the polar cap

Abstract

AbstractA statistical analysis using a long‐term (over one solar cycle) photoelectron data set obtained by the Fast Auroral SnapshoT satellite demonstrates that photoelectron outflows has little impact on the polar wind ion flux. This result implies that it is the source region of H+ ions in the topside ionosphere and not the photoelectron flux that controls the terrestrial polar wind flux. The polar wind ion flux, estimated from electron outflow does not change with increasing net photoelectron production due to increasing solar activity. The magnitude of a self‐created field‐aligned potential drop is likely determined so as to equilibrate electron fluxes with ion fluxes regulated by a net production rate of H+ ions. The result suggests that the polar wind H+ ion flux from magnetized terrestrial planets, including Earth‐like exoplanets, can be estimated once the composition and temperature of its atmosphere, which determine the net ion production rate, are known.