Evaluation of ionospheric profilers using topside sounding data



An operational system for deducing and imaging the vertical distribution of the electron density in the local ionosphere has been recently developed. The electron density profile is deduced from combined ground-based measurements of the total electron content, ionospheric vertical incidence soundings, and empirically obtained values of the O+-H+ ion transition height. The topside profile is permitted to take one of several forms: Exponential, Chapman, or Epstein. An evaluation of the above mentioned ionospheric profilers is needed in order to determine which one of them provides the best representation of the current ionospheric conditions. For this purpose, we use electron density profiles obtained from ionograms recorded by the topside sounders onboard the Alouette and ISIS satellites. Every profile has been fitted with each of the above mentioned theoretical ionospheric profilers and the corresponding approximation errors calculated. The results have been analyzed with respect to local time, geomagnetic latitude, season, magnetic and solar activity, ion transition height, and the ionospheric density peak characteristics. It has been found that, in the majority of cases, the best fit is provided by the exponential profiler, followed by the Chapman profiler. Also, while some influence of the underlying physical drivers on the topside electron density profile is detected, it is the use of ionospheric characteristics that offers more reliable selection criteria for the most appropriate profiler.