Simulating Plasmasphere Field-Aligned Density Profiles Measured with IMAGE/RPI: 
Effects of Ion Heating and Refilling 

Tu, J., Horwitz, J.L., Song, P., Huang, X., Reinisch, B.W., Richards, P.G. 


The Radio Plasma Imager (RPI) on board the IMAGE satellite measured a set of 
plasma density profiles along the magnetic line from L = 2.51 to 3.23 on June 8, 
2001, about seven days after a magnetic disturbance. We simulate these density 
profiles using a time-dependent field line interhemispheric plasma (FLIP) model 
and compare the modeled density profiles with the observed ones. We find that 
appropriate consideration of refilling stage and possible direct ion heating in 
the plasmasphere during the refilling process, in addition to heating through 
Coulomb collisions with the hotter plasmaspheric electrons, allows the simulated 
density profiles to attain close agreement with those measured by the RPI 
instrument. The enhanced ion pressure in the plasmasphere due to the ion heating 
impedes the ionospheric inflow from both hemispheres toward the equator, giving 
rise to a decreased amount of ionospheric ions to be transported to the 
equatorial region. The plasmasphere refilling rate is thereby reduced by the 
effects of the localized ion heating. The present study corroborates the idea 
that direct ion heating can significantly affect the plasmaspheric density 
structures. 

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Presented at the 2002 Spring A.G.U. Meeting, 
Washington, D.C., U.S.A., 28-31 May 2002