Statistical Properties of Mesoscale Plasma Flows in the Nightside High‐Latitude Ionosphere

Abstract

AbstractThe field of space weather has made great strides in understanding and simulating large‐scale, global responses of the Earth's upper atmosphere to various inputs from the Sun; however, the mesoscale phenomena (~30–500 km wide) that are much more dynamic and powerful in the coupled system have remained uncharacterized. We therefore present key parameters of mesoscale ionospheric plasma flows in order to evaluate their relationship within the coupled system and to inform global models. We characterize mesoscale plasma flow properties in the nightside polar cap and auroral oval using nine years of Super Dual Auroral Radar Network (SuperDARN) line‐of‐sight velocity data from the stations at Rankin Inlet and Saskatoon. We quantify their width, velocity, occurrence rates, duration, and orientation, and how these characteristics depend on latitude, magnetic local time (MLT), season, substorm activity (AL), solar cycle (F10.7), and interplanetary magnetic field (IMF) clock angle. Measuring the ionospheric footpoint of magnetospheric fast flows, our analysis technique from the ground also provides a 2‐D picture of flows and their characteristics that spacecraft alone cannot provide. Results include a characteristic equatorward flow width of ~180 km in the polar cap and ~140–150 km in the auroral oval. Flow velocities vary under the different conditions we studied. Equatorward polar cap flows and poleward flows everywhere have a postmidnight preference, suggesting a connection to polar cap arcs. Equatorward auroral oval flows have a premidnight preference, suggesting a connection to substorm‐related phenomena. The location and orientation of mesoscale flows dependent on IMF clock angle suggests that mesoscale flows follow the large‐scale background convection.