Collective scattering of electromagnetic waves in the presence of suprathermal electrons

The density fluctuation spectrum, resulting from a collective (k lambda _De<1) scattering process of electromagnetic waves in a plasma characterized by the presence of suprathermal electrons, has been computed in the high-frequency interval, omega approximately= omega _pe, omega _ce. It turns out that the amplitude of the resonant line, around the upper hybrid frequency, is amplified with respect to the thermal case, for those electrostatic oscillations propagating almost perpendicularly to the magnetic field. Moreover, the enhancement factor is given by the ratio between the average suprathermal energy and the plasma temperature, independently of the relative number of the energetic electrons. This peculiarity allows one to obtain useful information about the local spatial distribution of the energy of the suprathermal electrons and, if combined with ECE measurements, on their density distribution.