Unexpected STEVE Observations at High Latitude During Quiet Geomagnetic Conditions

Strong Thermal Emission Velocity Enhancement (STEVE) is a fascinating optical phenomenon typically observed in the mid-latitude ionosphere. Recent observations reveal an exceptional STEVE event occurring at high latitudes, approximately 10 degrees poleward of previously documented cases. This event, recorded in Yellowknife, Canada, by a TREx RGB imager and a citizen scientist, coincided with Swarm satellite measurements of extreme westward ion drift velocities exceeding 4 km/s. Such velocities are generally associated with subauroral regions at mid-latitudes, making this high-latitude occurrence particularly striking.
Notably, this event unfolded in the absence of a substorm, a departure from previous STEVE and extreme drift velocity observations. High-latitude radars detected rapid equatorward ionospheric flows, while GOES satellites recorded no particle injections, suggesting a highly inflated inner magnetosphere.
This unique case study challenges existing paradigms of subauroral dynamics and highlights the significant influence of magnetospheric configurations on ionospheric responses. In this talk, we will discuss the characteristics of this event and examine the associated solar wind, magnetosphere, and ionosphere interactions.