Circumpolar ground‐based optical measurements of proton and electron shock aurora

Abstract

AbstractMeridian scanning photometer (MSP) data are combined with global ultraviolet images from the Polar Ultraviolet Imager instrument to estimate the timing and propagation speed of shock auroras previously studied using solely space‐based ultraviolet auroral imagery. The multispectral nature of the MSPs, including the presence of a Balmer beta channel, enables the discrimination between proton and electron aurora. Following a near‐magnetic noon onset, the occurrence of auroral emissions created by shocked precipitating protons and electrons is observed to propagate tailward, along the auroral oval with speeds of several km/s, consistent with the shock propagation speed in the solar wind. In two cases, shock aurora propagation speeds along the auroral oval determined from satellite imagery are confirmed, to within calculated uncertainties, with ground‐based timing. The majority of instruments detect low‐energy discrete auroral arcs poleward of diffuse, higher‐energy aurora. Evidence of a previously reported two‐pulse proton aurora shock onset is detected at some, but not all, locations.