Is EISCAT able to determine H + temperature and velocity? Numerical simulation

• Published in: Journal of atmospheric and terrestrial physics 1996, Vol.58 (1), p.287-295
• Main Authors: Diloy, P.-Y., Fontanari, J., Alcaydé, D., Lovhaug, U.P., van Eyken, A.P.
• Format: Article
• Language: English
• ISSN: 0021-9169
• DOI: 10.1016/0021-9169(95)00036-4

Previous studies of the escape of the light ion H + using the EISCAT-VHF radar have demonstrated that there is substantial interest in measurements of the temperature and vertical velocity of this ion. In the altitude range of the polar ionosphere probed by the radar, the relative abundance of H + ions may reach large enough values to allow the determination of H + temperature and velocity from the effect on the shape of the scattered spectra. In order to prove that it is possible to deduce the temperature and velocity of this minor ion, a two step numerical simulation has been performed. Since it is hopeless to determine seven ionospheric parameters simultaneously from the spectra, the first step was to establish the best sequence of analysis to estimate these parameters. Synthetic spectra have been used, based on realistic relative H + ions concentrations currently observed throughout the altitude range probed by the radar, to realize this study. For the first step, perfect spectra without any noise were analysed. In a second step, the procedure has been applied to similar synthetic spectra but with realistic signal-to-noise ratios (SNR) representative of present observations. The results of these simulations show that the determination of H + temperatures and velocities is a very difficult task and that it is only possible in a very limited altitude range where both the H + concentration and the signal-to-noise ratio are large enough.