An ISEE/Whistler model of equatorial electron density in the magnetosphere

Attention is given to an empirical model of equatorial electron density in the magnetosphere covering the L range 2.25-8. Although the model is primarily intended for application to the local time interval 00-15 MLT, a way to extend the model to the 15-24-MLT period is presented. The model describes, in piecewise fashion, the 'saturated' plasmasphere, the region of steep plasmapause gradients, and the plasma trough. Within the plasmasphere the model profile can be expressed as logne - Sigma-xi, where x1 = -0.3145L + 3.9043 is the principal or 'reference' term, and additional terms account for: a solar cycle variation with a peak at solar maximum; an annual variation with a December maximum; and a semiannual variation with equinoctial maxima.