F-region electron heating by X-mode radiowaves in underdense conditions

Abstract. Observations of modifications of the electron temperature in the F-region produced by powerful high frequency radiowaves at 4.04 MHz transmitted in X-mode are presented. The experiments were performed during quiet nighttime conditions with low ionospheric densities so no reflections occurred. Electron temperature enhancements of the order of 300–400 K were obtained. Numerical simulation of ohmic heating by the pump wave reproduces both altitude profiles and temporal dependence of the temperature modifications in the experiments.