Control of plasmaspheric dynamics by both convection and subauroral polarization
stream

J. Goldstein, B.R. Sandel, M.R. Hairston, and P.H. Reiff

The long-standing hypothesis that plasmaspheric dynamics are described by
superposition of corotation and solar-wind-driven sunward convection is tested
via direct comparison between plasmasphere observations and simulation output.
The observations consist of global plasmasphere images produced by the IMAGE
extreme ultraviolet (EUV) imager during plasmasphere erosion on 2 June 2001. The
simulation is a plasmapause evolution model driven by a time-varying
Volland-Stern (VS) electric potential distribution. On the dawnside and much of
the nightside the model matches the EUV plasmapause position to within 0.2Ð0.5
earth radii (RE). Near dusk the model plasmapause is about 0.7Ð1.2 RE farther
out than the EUV plasmapause, suggesting that an improved model should include
the duskside flow enhancement known as the sub-auroral polarization stream
(SAPS). We demonstrate that including a simplified ad-hoc SAPS potential can
correct the model on the duskside.

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Geophysical Research Letters, 30 (24), 2243, doi:10.1029/2003GL018390, 2003.