Determining the density and composition of plasma in the inner magnetosphere is a largely unexplored area of magnetospheric and ionospheric research. Using recently developed whistler mode (WM) radio sounding techniques and data from a new generation of space- and ground-based experiments, this three-year research program will investigate inner magnetospheric plasma density, ion composition and density irregularities from 90 to 5000km. Four research projects have been proposed: (1) Use WM radio sounding data from the Radio Plasma Imager (RPI) on the IMAGE satellite to measure the cold-plasma density (Ne), ion composition (H+, O+, He+) and density irregularities (10m to 10km scale size) along a magnetic field line as a function of geophysical conditions (e.g. location, local time, plasmapause position, geomagnetic and solar activity). (2) Study the variation (loss and refilling) of electron density and ion composition along geomagnetic field lines before, during, and after geomagnetic storms. (3) Build empirical models of plasma density, ion composition and density irregularities as functions of geophysical conditions along B0 from 90-5,000km. (4) Combine WM sounding results with those from complementary ground based (e.g. ionosonde, magnetometer), spacecraft based in situ (e.g. DMSP, CHAMP, CRESS, POLAR) and radio sounding (e.g. RPI sounding at higher altitude in free space modes) to augment and extend the empirical models and to build new field aligned models of the inner magnetospheric plasma density and composition up to equatorial altitudes. These empirical models will be used to gain new understanding into processes and mechanisms important to magnetosphere-ionosphere coupling and for use in space weather predictions. As a result these results should have broad application in space physics research. The proposal will support a graduate student.
