FAST SATELLITE WAVE OBSERVATIONS IN THE AKR SOURCE REGION

The Fast Auroral SnapshoT (FAST) satellite has made observations in th e Auroral Kilometric Radiation (AKR) source region with unprecedented frequency and time resolution. We confirm the AKR source is in a densi ty depleted cavity and present examples in which cold electrons appear ed to have been nearly evacuated (n(hot) > n(cold)) Electron distribut ions were depleted at low-energies and up-going ion beams were always present. Source region amplitudes were far greater than previously rep orted, reaching 2x10(-4) (V/m)(2)/Hz (300 mV/m) in short bursts with b andwidths generally < 1 kHz. Intense emissions were often at the edge of the density cavity. Emissions were near or below the cold plasma el ectron cyclotron frequency in the source region, and were almost entir ely electromagnetic. The \E\/\B\ ratio was constant as a function of f requency and rarely displayed any features that would identify a cold plasma cutoff or resonance.