ASYMMETRIC ELECTRON-CYCLOTRON EMISSION FROM NONTHERMAL PLASMAS SUBJECT TO A GENERALIZED KIRCHHOFFS LAW

The electron cyclotron emission (ECE) spectra characteristic of a non- thermal plasma comprising a current-carrying superthermal electron tai l, for which a generalized Kirchhoffs law holds true, are evaluated fo r both the extraordinary (X) and ordinary (O) mode, for perpendicular as well as oblique propagation on the outboard side of the plasma; bot h higher order finite-Larmor-radius effects and harmonic overlap are a ccounted for. Besides a spectrally narrow non-thermal feature occurrin g at frequencies downshifted to both first (in X and O-modes) and seco nd (X-mode only) harmonic cyclotron frequencies outside the plasma, th e non-thermal ECE contributes a spectrally broad enhancement to the th ermal emission, a salient characteristic of the non-thermal ECE being the asymmetry with espect to the parallel refractive index. The releva nce of the upshifted second harmonic ECE of the X-mode is discussed al ong with the concomitant downshifted third harmonic emission for both optically thick and optically thin plasmas.