On the Temporal Variability of High-Altitude Reflection Potential Structures (HARPS)

Abstract

High Altitude Reflection Potential Structures (HARPS) with typical magnitudes of a few tens of volts have been frequently detected above Earth's sunlit polar cap. They are thought to be electrostatic structures forming between 1 to several Earth radii in altitude. Previous satellite studies have been unable to probe the temporal variability of their magnitude owing to their fast motion through the region of observation. In this study, we present a $\sim$10 min time series of observations of HARPS from NASA's Endurance sounding rocket. These observations were made from a spatially localized region, enabling the first experimental investigation of the temporal variability of HARPS. The magnitude of the potential drop was found to vary unexpectedly rapidly between 15.5 and 23.7 V on a time cadence of $\le 10$ s. We additionally find an inverse correlation between polar rain precipitating flux and reflection potential magnitude, consistent with predictions from prior theoretical work.