Precipitation of auroral and ring current particles by artificial plasma injection

Outside the plasmasphere, most of the energy in magnetospherically trapped particles resides in two populations, auroral‐energy electrons and the proton ring current, with single‐particle energies from 1 to 50 kev. The ring current contains more energy than all other components of the magnetospherically trapped radiation. It may be possible to precipitate a large fraction of this energy into the ionosphere by injection of a light‐ion plasma from a synchronous satellite; this would render the ring current protons unstable to a variety of plasma modes. Auroral‐energy electrons can be precipitated by ions of any mass, but heavy (e.g., barium) ions will quench what may be the most important proton instability, which takes place in the electromagnetic ion cyclotron mode. This mode is unstable only if the ring current protons have an average velocity greater than the wave phase velocity. The wave speed varies as N −1/2 , where N is the cold plasma density; under natural conditions, N is too small for the ring current to be unstable outside the plasmapause. Injection of some tens of pounds of lithium ions at synchronous altitude will create an unstable region with a diameter of a few thousand kilometers; as a result of the instability, ring current protons will precipitate into the ionosphere at a rate up to 1 erg cm −2 sec −1 . This should produce important effects in the upper E and F layers of the ionosphere. At the same time, precipitating auroral‐energy electrons may create auroras and other effects usually associated with geomagnetic storms.