Modeling the ionosphere topside to plasmasphere electron density distribution
using ISIS and IMAGE/RPI satellite data

Bodo W. Reinisch, Patrick Nsumei, Xueqin Huang, and Dieter Bilitza


We represent the F layer topside Ne profile from hmF2 to the plasmasphere by an
a-Chapman like function with a Chapman scale height H(h) that varies
continuously with height. This profile function is called a vary-Chap function.
For given F2 peak values foF2 and hmF2, we find H(h) by fitting the vary-Chap
function to Ne(h) profiles measured by the ISIS topside sounders.  Our initial
results show that H(h) at the F2 peak is almost constant with height; a rapid
increase occurs ~300 to 900 km above hmF2, reflecting the O+ to light-ion
transition. A hyperbolic tangent function suitably represents this variation,
and allows the parameterization of the scale height function in terms of the
transition height hT, the scale height HT at hT, and the steepness of the
transition, b. We explore two different approaches to determine these
parameters. One is to find the vary-Chap functions that smoothly interpolates
between plasmasphere profiles and the F2 layer peak. Measurements by the Radio
Plasma Imager (RPI) on the IMAGE satellite provide plasmasphere profiles down to
~3000 km altitude [Reinisch et al., Plasma Density Distribution Along the
Magnetospheric Field: RPI Observations from IMAGE, Geophys. Res. Ltrs., 28, 24,
4521-4524, 2001]. For the F2 peak we use the IRI profiles [Bilitza, D.,
International Reference Ionosphere 2000, Radio Science 36, #2, 261-275, 2001].
The other approach makes a least-squares fit of vary-Chap functions to topside
profiles measured by the ISIS topside sounders [Huang et al., Electron Density
Profiles of the Topside Ionosphere, Annali di Geofisica, 45 (1), 125-130, 2002]. 

_______________
Spring Joint Assembly, American Geophysical Union, Baltimore, Maryland, U.S.A., 
23-26 May 2006