High-resolution observations of convection structure related to Poleward Boundary Intensifications and Auroral Streamers using SuperDARN and Allsky Imagers.

Abstract:

A new technique for analysis of SuperDARN convection observations enables resolving plasma convection with unprecedented spatial resolution. The technique, Local Divergence-Free Fitting (LDFF), can be used to produce maps of a spatial resolution that is determined by the resolution and quality of the observations rather than the fit order. The LDFF technique is described and then applied to observations from an interval during which auroral observations over Alaska were obtained. A detailed comparison is carried out between the high-resolution convection maps and the auroral images. In the interval, Poleward Boundary Intinsifications (PBIs) were observed that developed into auroral streamers and subsequently reached the euqatorward boundary of the main auroral oval. Brightening of the equatorward-most arc and an auroral expansion followed the second streamer reaching the equatorward-arc latitude. The LDFF shows plasma flow in the region of the PBI and streamer with a region of shear across the arcs that propagates with them. The shear precedes (in time) the auroral brightness and diminishes as the brightness decreases. The relationship of the flows to the local field-aligned currents and the larger-scale convection are examined.