Two-dimensional ionospheric flow pattern associated with auroral streamers

Abstract

We present direct two-dimensional flow observations and auroral images from the Super Dual Auroral Radar Network (SuperDARN) radar and Wideband Imaging Camera onboard Imager for Magnetopause-to-Aurora Global Exploration (IMAGE/WIC) imager to investigate the ionospheric flow pattern associated with auroral streamers for four events. Using the SuperDARN observations allows us to observe the flow associated with the streamers in the context of the larger-scale background convection. For all four cases studied, streamers developed from preexisting east-west (EW) arcs that initiated from bead-like or small-scale auroral intensifications around the auroral poleward boundary. We find a vortex-like flow pattern with clockwise sense surrounding both the initial auroral forms and the ensuing streamers. We also found in three cases signatures of flow bifurcations at the equatorward end of the streamers, which suggests a double vortex-like flow pattern with the counterclockwise vortex east of the clockwise one. Our results are consistent with the double-vortex flow structure that results from interchange convection associated with a plasma sheet bubble predicted by different numerical simulations. This supports several previous studies and offers more complete observational evidence that the observed flow pattern may be the ionospheric manifestation of interchange instability in the plasma sheet. Copyright 2012 by the American Geophysical Union.