Quoted from: https://ccmc.gsfc.nasa.gov/modelweb/plasmas/webb.html

Parameter: O+ and H+ densities and plasma temperatures in the plasmasphere

Brief Description:
The Global Plasmasphere Ionosphere Density (GPID) model uses a simplified theoretical approach based in part on diffusive equilibriumto describe the density of the main ions (O+, H+) and the electron temperature in the plasmasphere along a magnetic flux tube. GPID assumes an ionosphere=plasmasphere composition of O+ and H+, and includes chemical processes and simple diffusive transport. Comparisons between GPID and the refilling fluxes obtained from whistler observations generally show good agreement, both in diurnal variations and during prolonged refilling of empty flux tubes. Comparisons to seasonal variations during solar maximum at L=2.5 show good agreement with observations, but at solar minimum there is variable agreement. The model uses the IRI model for its base point of 350 km and below. A weighting function is used that allows the H+ profiles to be smoothly converted from diffusive control to chemical control in the upper ionosphere.This approach avoids the problem of hemispherical density mismatch, which normally occurs at the field line apex when diffusive equilibrium calculations are used to extrapolate ion densities up the field line from the two hemispheres. Availability: Please contact model authors.

References:
P.A. Webb and E.A. Essex, A dynamic diffusive equilibrium model of the ion densities along plasmaspheric magnetic flux tubes, J. Atmos. Solar-Terr. Phys. 63, 1249-1260, 2001

P.A. Webb and E.A. Essex, Modifications to the Titheridge upper ionosphere and plasmasphere temperature model, J. Geophys. Res. 108, A10, 1359, doi:10.1029/2002JA009754, 2003