IS EISCAT ABLE TO DETERMINE H- NUMERICAL-SIMULATION( TEMPERATURE AND VELOCITY )

Previous studies of the escape of the light ion H+ using the EISCAT-VH F radar have demonstrated that there is substantial interest in measur ements of the temperature and vertical velocity of this ion. In the al titude range of the polar ionosphere probed by the radar, the relative abundance of H+ ions may reach large enough values to allow the deter mination of H+ temperature and velocity from the effect on the shape o f the scattered spectra. In order to prove that it is possible to dedu ce the temperature and velocity of this minor ion, a two step numerica l simulation has been performed. Since it is hopeless to determine sev en ionospheric parameters simultaneously from the spectra, the first s tep was to establish the best sequence of analysis to estimate these p arameters. Synthetic spectra have been used, based on realistic relati ve H+ ions concentrations currently observed throughout the altitude r ange probed by the radar, to realize this study. For the first step, p erfect spectra without any noise were analysed. In a second step, the procedure has been applied to similar synthetic spectra but with reali stic signal-to-noise ratios (SNR) representative of present observatio ns. The results of these simulations show that the determination of H temperatures and velocities is a very difficult task and that it is o nly possible in a very limited altitude range where both the H+ concen tration and the signal-to-noise ratio are large-enough.