Convection Plasma Drifts in the Inner Magnetosphere Associated with a 
Plasmaspheric Drainage Plume 
 
Chin. S. Lin, Huey-Ching Yeh, Bill R. Sandel, J. Goldstein, Frederick J. Rich, 
William J. Burke, and J. C. Foster 
 

We report first observations of equatorial convection signatures associated with
a plasmaspheric drainage plume using multi-satellite simultaneous observations. 
The Extreme Ultraviolet (EUV) sensor on board the IMAGE satellite observed a
plume extending outward to L  2.8 near 16 - 17 magnetic local time (MLT) during
the recovery phase of the 2000 Bastille Day magnetic storm. The plasmaspheric
boundary was near L = 2 at other local times.  We mapped simultaneously measured
ionospheric plasma drifts from ROCSAT-1 and three Defense Meteorological
Satellite Program (DMSP) spacecraft along magnetic field lines to infer ion
convective velocities near the equatorial plane of the inner magnetosphere.  The
zonal component of convection derived from ROCSAT-1 ion-drift measurements
manifests sharp positive azimuthal gradients in the vicinity of plume
boundaries, reversing direction from westward to eastward.  ROCSAT-1 also
detected upward field-aligned flow, suggesting that plasmasphere refilling is
associated with the sharp zonal velocity gradient.  The meridional profile of
horizontal velocities deduced from DMSP measurements shows a large flowing
westward sub-auroral polarization stream (SAPS) located outside the plasmapause.
 The peak of SAPS was centered at about the radial distance of L= 2.8 with a
full-width of about 1 RE.  In EarthÕs frame of reference, equatorial plasmas
flow toward the plume from both the dayside and evening sides of the plume,
suggesting a negative azimuthal gradient in the equatorial azimuthal velocity. 
The azimuthal velocity gradient was largest at the radial distance of the
plumeÕs outermost boundary.  These observations provide new evidence about
diversion of SAPS plasma flows and distinct signatures of azimuthal velocity
reversal in the vicinity of plasmaspheric plumes.

_______________
Submitted to Journal of Geophysical Research