Specifying Plasma Density Profiles for Plasmasphere Refilling Using IMAGE RPI 
Observations

Jiannan Tu, Paul Song, Bodo W. Reinisch, James L. Green, Xueqin Huang


Ducted echoes observed by the radio plasma imager (RPI) on the IMAGE satellite
are used to derive the field-aligned electron density profiles in the nightside
plasmasphere and plasma trough for three plasmasphere passes. It is determined
that the density profiles of the saturated (in the inner plasmasphere) and
depleted (in the plasma trough or outer plasmasphere) flux tubes are of
different field line dependence. A multi-variant least square fit technique with
a simple functional form is utilized to fit those density profiles. The
functional form has several free parameters that define the field line
dependence of the density profile, i.e., the steepness of the density profile at
high latitudes and flatness at low latitudes, as well as the equatorial density.
In each pass the saturated and depleted flux tubes can easily be fitted with
this functional form, with a different set of values of the fitting parameters
for the two groups (saturated and depleted) of flux tubes and different
equatorial density for each individual density profile. The results imply that
we may reasonably specify the density profiles along the depleted flux tubes for
plasmasphere refilling studies by specifying the field line dependence and the
equatorial density level of the density profiles.

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Fall Meeting, American Geophysical Union, San Francisco, U.S.A., 2005