Coordinated Swarm in Situ and THEMIS All Sky Imager (ASI) Observations of the Motion of Patchy Pulsating Aurora

Abstract:

Patchy pulsating aurora (PPA) is a common ionospheric phenomenon. In an earlier statistical study using THEMIS-ASI observations, we have shown that the PPA mainly drift eastward after midnight and westward before midnight suggestive of the drift velocity of the patches is tied to convection (E × B drift). Comparing patch velocities inferred from THEMIS-ASI image sequences and ionospheric convection inferred from SuperDARN data, we found out that in four events, the PPA patches were moving at the local convection velocity, within experimental error. Due to uncertainties in inferring convection velocity from the SuperDARN measurements, we need to check this result. Here, we compare patch velocities inferred from THEMIS-ASI data with drift velocities in the topside ionosphere measured by the ESA Swarm satellites. Our results corroborate those of our earlier studies, and we assert that PPA motion is EXB convection. Given that the processes that define the shape of PPA patches occur near the magnetospheric equator, our results indicate that cold magnetospheric plasma plays a key role in determining patch shape and evolution. Further, our results point the way to remote sensing equatorial convection in the inner magnetosphere from images of PPA.