Ionospheric Plasma Circulation Associated with Polar Cap Arcs Detached from the Auroral Oval

Abstract:

Joint observations of the OMTI all-sky camera at Resolute Bay, NWT (Canada), the SuperDARN radars and Swarm satellites are considered to investigate horizontal plasma flows and vertical field-aligned currents (FACs) associated with polar cap arcs “detached” from the auroral oval but not penetrated deep into the polar cap. All cases are for the near winter solstice, positive IMF Bz and mostly dominating IMF By. We show that the arcs are usually co-exist with strong flow shears driven by electric fields of the converging type. The shears, being added to the background flow, produce unusual convection patterns, for example reverse (sunward) flows on the nightside, several MLT hours away from the noon-midnight line. We also investigate the distribution of FACs in the arcs’ vicinity, both duskward and dawnward, for several Swarm passes. Electron density data onboard Swarm satellites are used to identify the arc and auroral oval boundaries, along with the ground-based optics. The data suggest that the arcs correspond to a separate current system excited in addition to the background plasma circulation governed by the reconnection processes.Joint observations of the OMTI all-sky camera at Resolute Bay, NWT (Canada), the SuperDARN radars and Swarm satellites are considered to investigate horizontal plasma flows and vertical field-aligned currents (FACs) associated with polar cap arcs “detached” from the auroral oval but not penetrated deep into the polar cap. All cases are for the near winter solstice, positive IMF Bz and mostly dominating IMF By. We show that the arcs are usually co-exist with strong flow shears driven by electric fields of the converging type. The shears, being added to the background flow, produce unusual convection patterns, for example reverse (sunward) flows on the nightside, several MLT hours away from the noon-midnight line. We also investigate the distribution of FACs in the arcs’ vicinity, both duskward and dawnward, for several Swarm passes. Electron density data onboard Swarm satellites are used to identify the arc and auroral oval boundaries, along with the ground-based optics. The data suggest that the arcs correspond to a separate current system excited in addition to the background plasma circulation governed by the reconnection processes.