Research of Ionospheric Instability Excited in Mid and Low Latitudes HF Heating

Abstract

AbstractThe results of 2D simulation of ionospheric HF pump heating indicate that although the simulation results are affected by the background ionospheric conditions, the electron density and temperature tend towards stationary after heating simulation begins under most undisturbed circumstance. This result is proved by many experiments. Nevertheless on occasion the temporal and spatial distribution of the electron density and temperature near the reflection region of HF pump waves appear to be instable after turning on/off the HF heating equipment. This phenomenon is simulated and interpreted in this paper. The excitation of this instability is explained by a positive feedback mechanism as follows, when the electron temperature is heating up by the pump waves, the reduction of electron density in this region is generated by the plasma expansion. The electron energy decreases in the electron energy equation due to the collision between electron and ion which is influenced by the electron temperature and density. In consequence the positive feedback mechanism is set up as a result of electron temperature increase. It can be concluded that a more obvious change of electron density and temperature in HF pump heating is generated by an instability mechanism if three conditions are satisfied, (1) an evident two‐peak structure of ionospheric electron temperature; (2) a high electron temperature in the heated region; (3) electron and ion collision is the main proportion of the energy loss factor. These conditions are more easily to be satisfied in the afternoon. Key words Hight Frequency (HF) heating, Mid and low latitude ionosphere, Instability, Simulation