The emissivity of the perpendicular extraordinary mode around the fundamental electron cyclotron resonance is investigated for loss-cone type distribution functions having high average kinetic energy. Both a Dory-Guest-Harris (DGH) type distribution and a loss-cone (LC) distribution with rounded edges are considered. The emissivity is calculated both using the usual equation for the emissivity and (in the case of the DGH distribution) using a modified Kirchhoff's Law. The results are presented in terms of an appropriately normalized emissivity and show a remarkable feature, namely, sharp peaks in the emissivity are found for frequencies and plasma parameters for which either a cut-off or a resonance occurs. This result is explained by the fact that the (normalized) emissivity is inversely proportional to the energy flux (normalized to the square of the electric field of the waves) in the direction of the wave vector, such a normalized energy flux going to zero both at a cut-off and at a resonance. No qualitative differences are found for the two types of distribution functions.
Characterization of the electron distribution function in an electron-cyclotron driven toroidal plasma