10/14/2011 - Ionospheric flow patterns associated with poleward boundary intensifications (PBIs)


3:30 PM - 6:00 PM
6704 Geology

Presented By:
Yong Shi - UCLA AOS


We present direct two-dimensional (2-d) flow observations and auroral images from the SuperDARN radar and IMAGE WIC imager to investigate the ionospheric flow pattern associated with PBIs and auroral streamers. Using the SuperDARN observations allows us, for the first time, to observe the flow associated with the streamers in the context of the full background convection. For the streamer cases studied, streamers developed from 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 one further east of the clockwise one. Our results are consistent with the double-vortex flow structure due to interchange convection associated with a plasma sheet bubble predicted by different numerical simulations, and also provide solid evidence to several previous studies, especially Sergeev et al. [2004], that have attempted to establish the relationship between streamers and tail interchange convective flows. In short we offer more complete evidence that the observed flow patterns may be the ionospheric manifestation of interchange instability in the plasma sheet. For the PBI case studied, similar flow pattern have been found, i.e. vortex-like flow shear surrounding the PBI auroral form at the poleward boundary. Some PBIs develop into streamers and some just stay around the poleward boundary. The follow pattern is nearly identical. We also find an association of longitudinally structured polar cap flow enhancements with the initiation of PBI.

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