This project will study plasma density distributions and dynamics in the near-earth magnetosphere (plasmasphere, sub-auroral/auroral and polar cap region) by using data from the Radio Plasma Imager (RPI) on the IMAGE satellite. The active radio sounding of the RPI provides local plasma resonances and remotely reflected signals (echoes) that can be used to derive plasma densities in-situ at satellite locations, and remotely and instantaneously the density distributions along the magnetic field lines down to the altitude as low as approximately 3000 km. The RPI database has accumulated about one million measurements covering all local times from about 3000 km to 4 Re altitude under different geomagnetic activities and the database is still growing. This makes it possible to develop empirical density models as function of radial distance, latitude, local time, season, solar wind/interplanetary magnetic field (IMF) conditions, and geomagnetic activity indices. The RPI empirical models will be compared with topside density profiles from the International Reference Ionosphere (IRI). The statistical and event observations, as well as numerical simulations, will be utilized to provide insights to the plasma dynamics both for the average density distributions and actual events.
