Ground-Based / Image Observations of the Redistribution of the Stormtime
Ionosphere and the Formation of the Plasmaspheric Bulge

J. Foster (MIT Haystack Observatory, Westford, MA 01886)

Disturbance electric fields uplift and redistribute low-latitude thermal
plasma producing a pronounced poleward shift of the equatorial anomalies (EA).
This effect is most pro-nounced in the vicinity of the South Atlantic magnetic
anomaly, producing greatly-enhanced total electron content (TEC) at low mid
latitudes (near L=2) and deep TEC depletions at the magnetic equator during
extreme geomagnetic storm conditions. Ground-based GPS propagation data
produce two-dimen-sional TEC maps of the equatorial anomaly region. DMSP
satellite overflights provide in-situ density and plasma flow/electric field
observations. The Millstone Hill radar, looking far equatorward to the edge
of the perturbed plasmasphere near L=2, observes the uplift of the F-layer
peak altitude and the downward and poleward flow of thermal plasma into the
topside F-region associ-ated with the poleward spread of the EA peaks.
Simultaneous 2-D observations of the evolution of the enhanced EA region using
GPS TEC and IMAGE FUV observations reveal the spatial extent and temporal
evolution of this phenomenon. 

Seen both from the ground and from space, the poleward redistribution of
low-latitude thermal plasma into the spread EA region forms a bulge in the
dusk-sector plasmapause boundary layer (PBL). This high-TEC thermal plasma
then co-rotates with the Earth and is eroded by the sub-auroral polarization
stream (SAPS) electric field. The eroded material is carried across the
mid-latitude region as plumes of storm-enhanced density (SED) which produce
considerable space weather effects across the North American continent. The
SED plumes mark the ionospheric foot-print of the sunward-streaming
plasmasphere drainage plumes observed with IMAGE EUV.

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Presentation at the Yosemite Conference of Inner Magnetospheric Interactions,
3 - 6 February 2004, Yosemite, California, USA