On the properties and origin of the Venus ionosphere

Abstract

The brief review of the properties of dayside and nightside ionosphere of Venus is given, and some possible origins of ionization are discussed. There are arguments in favour of the impact ionization by electrons from magnetotail as the source of main ionization peak of the nightside ionosphere. The discrepancies in the results obtained by the different in-situ experimental techniques, as well as the discrepancies between the in-situ experimental results and radio occultation results, do not allow the Venus ionosphere to be described quantitatively (although the qualitative description seems to be possible). After Venera-9, −10 and Pioneer-Venus experiments, a great number of publications followed which dealt with experimental data, hypotheses and theoretical models. They described some properties of Venus' ionosphere as well as its origin. Measurements of the same properties made by different methods often gave inconsistent results. Models based on various preconditions had both common and different features. Finally hypotheses of ionization sources, especially in the night ionosphere, are still under discussion. It is of interest to analyze the available publications about the properties and origin of Venus' ionosphere emphasizing the inconsistent and debatable results in order to argue for the necessity of statistically processing the available information, its averaging and tabulation for VIRA.