Magnetospheric model of subauroral polarization stream

J. Goldstein, J.L.Burch, B. R. Sandel


We present a magnetospheric model of the subauroral polarization stream (SAPS)
electric potential, parameterized by Kp index (valid for Kp = 4Ð7), based on a
previous study of the average characteristics of SAPS. The model treats the SAPS
westward flow channel as a potential drop whose radial location and width
decrease as a function of both increasing magnetic local time (MLT) and
increasing Kp. The magnitude of the SAPS potential drop decreases eastward
across the nightside, and increases with increasing Kp. The model SAPS flow
channel significantly alters the flow paths of plasma in the afternoon and
evening MLT sectors, and agrees with an earlier single-event study that used an
ad-hoc SAPS potential to obtain good agreement with plasmasphere observations.
The model performance is tested via comparison with 13 intervals of plasmapause
data obtained during the period 1 April through 31 May 2001 by the extreme
ultraviolet (EUV) imager on the Imager for Magnetopause-to-Aurora Global
Exploration (IMAGE) satellite. Although the model performs well, the current
Kp-based parameterization is somewhat crude, capturing only the gross spatial
and temporal SAPS characteristics. 

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Journal of Geophysical Research, in press, 110, doi:10.1029/2005JA011135, 2005