Polar Cap Boundary Identification Using Redline Optical Data and DMSP Satellite Particle Data

The location of the polar cap boundary is typically determined by using low-orbit satellite measurements in which the boundary is identified by its unique signature of a sharp decrease in energy and particle flux poleward of the auroral oval. In principle, this decrease in precipitating particles should appear as a concomitant sharp change in auroral luminosity. Based on a few events, Blanchard et al. (1995, ) suggested that a dramatic gradient in redline aurora may also be an indicator of the polar cap boundary. In recent years, advances in capabilities and the deployment of ground-based all-sky imagers have ushered in a new era of auroral measurements. Auroral imaging has moved well beyond the capabilities of the instrumentation in the previous study in terms of both spatial and temporal resolution. We now have access to decades of optical data from arrays spanning a huge spatial range, enabling a fresh examination of the relationship between redline aurora, particle precipitation, and the polar cap open closed boundary. In this study, we use data from the Defense Meteorological Satellite Program satellites in conjunction with the University of Calgary's Redline Emission Geospace Observatory (630.0 nm) data to assess the viability of automated detection of the 2-dimensional polar cap boundary. Our results exhibit good agreement between the optical and particle polar cap boundary and suggest that a luminosity in redline emission could serve as a reasonable proxy for the location of the electron poleward boundary, while providing both high temporal and spatial resolution maps of the open-closed boundary.