THE ELECTRON-CYCLOTRON MASER IN HOT THERMAL PLASMAS

We investigate the possibility of an electron cyclotron maser operatin g in a hot (T > 10(7) K) thermal plasma with a loss cone. We find that the instability can occur in this scenario because resonance involvin g electrons in the thermal tail can give rise to significantly large g rowth rates. We estimate the range of electron velocities that can be in resonance and show how this dictates the frequency and angular dist ribution of the emitted radiation. In so doing, we show quite generall y that it is the range of speeds and not the details of the loss cone edge, as previously thought, that determines the frequency and angular distribution. By considering the energetic constraints on the initial and final (i.e. when the maser is saturated) electron distributions, we estimate bounds on the energy that may be emitted. This energy can be a sizeable fraction (up to 5-10%) of the plasma electrons' total th ermal energy, though this is sensitively dependent on the temperature, density and magnetic field. Finally, we discuss the implications of t his emission for flaring solar coronal loops and hot stellar atmospher es.