Whistler mode radio sounding from IMAGE of field aligned electron and ion densities in the plasmasphere below 4000 km

Whistler mode sounding from IMAGE is a unique and novel method that permits remote sensing of field aligned electron density and ion composition in the altitude range 90-4000 km. These measurements are not possible with topside radio sounders utilizing other plasma wave modes. We present results from the radio sounding of the plasmasphere. Preliminary analysis of more than 250 cases of whistler mode echoes observed on IMAGE was performed to obtain: (1) dayside and nightside distribution of electron and H+, O+, and He+ ion densities in the L-shell range 1.6 to 4 during geomagnetically quiet to moderate conditions, and (2) variations in electron and ion densities as a function of geomagnetic storm activity. The results from whistler mode sounding will lead to new empirical models of field aligned electron and ion densities within the plasmasphere as a function L-shell, MLT, and geomagnetic activity. These models can be used to build as well as to test physics based models of the ionosphere and plasmasphere and of the coupling between the two and the underlying thermosphere.