e-POP Satellite Observations of Ion Upflow over Pulsating/Diffuse Aurora

Abstract:

The Enhanced Polar Outflow Probe (e-POP) satellite was launched by SpaceX on September 29, 2013 into a polar orbit. Near magnetic midnight on March 3, 2014, e-POP traversed a region of pulsating aurora over eastern Canada. Here, we present an analysis of in-situ optical, ion, electron, and magnetometer data recorded by instrumentation onboard the e-POP satellite in conjunction with ground-based observations. The observed small-scale field aligned currents (FAC) and soft electron precipitation suggest a Type II ion upflow event which occurred in coincidence with the pulsating aurora. In the Type II ion upflow process, precipitating electrons collisionally heat background electrons at lower altitudes, causing them to expand upward adiabatically. This expanding electron gas produces an electron density gradient, which gives rise to an ambipolar electric field that then accelerates ions to higher altitudes where they may be further energized by wave-particle interactions. Features in this event are similar to those of Kenward et. al. (2020), who have recently presented ground-based observations of Type II ion upflow alongside pulsating auroral signatures in Poker Flat Incoherent Scatter Radar (PFISR), and All Sky Imager data. Of particular interest in both events are the small-scale FACs and soft electron precipitation that occur alongside red aurora.