Quiet-Time Rapid Subauroral Plasma Flows at High Northern Magnetic Latitudes in the Dusk Sector

Rapid subauroral flows occurring at unusually high magnetic latitudes during quiet times and weak substorms are rarely investigated and poorly understood. We investigated the phenomenon in a comprehensive way by using multi-instrument and multipoint satellite observations along with a set of computed variables. We specified 5 Subauroral Polarization Streams (SAPS) and 28 Subauroral Ion Drifts (SAID) events observed in the Northern Hemisphere by spacecraft F18 in 2013. Driven by the strong poleward SAPS-SAID electric (E) fields (90–190 mV/m), high-latitude SAPS-SAID flows reached supersonic velocities (2400-5200 m/s) and developed at unusually high (≥68o) magnetic latitudes, in the dusk sector, sometimes on the dayside. The high-latitude SAPS/SAID flows appeared in the deep main trough and mostly within the downward region-2 current suggesting their previous development. Their underlying vertical upward/downward drifts, driven by eastward/westward zonal E fields, imply positive feedback mechanisms in progress. Earthward energy depositions into the high-latitude SAPS and SAID channels indicate magnetospheric electromagnetic energy generations in their respective voltage generators. Conjugate observations demonstrate the development of large outward SAID E field (EX≈10 mV/m) on 28 October 2013 and SAPS E field (EX≈10 mV/m) on 14 October 2013 at L≈10 RE on a short timescale at dusk.