Storm Time Mesoscale Plasma Flows in the Nightside High-Latitude Ionosphere: A Statistical Survey of Characteristics

Abstract

Although much work has been done to characterize the global response of Earth's upper atmosphere to geomagnetic storms, much is unknown regarding the response on mesoscales (~30–500 km). In order to understand how the nightside, high-latitude ionosphere responds on these scales during storms, we have characterized widths, velocities, and occurrence rates of equatorward and poleward mesoscale flows. We characterized them according to main phase versus recovery phase as well as coronal mass ejection (CME) versus high-speed stream (HSS) storms. Some results include the following: Mesoscale flows are faster during the main phase of the storms. Faster flows >400 m/s are more frequent and probable during CME storms as compared to HSS storms, but more flows occur during HSS storms. Polar cap flows are wider during CMEs than during HSSs. There is a postmidnight preference for polar cap mesoscale flows during storms, especially during recovery phase and during HSSs.