Ionospheres and atmosphere of non-magnetic planets and solar wind interaction: Part I - Venus

The solar-planetary interaction is unique for non-magnetic planets, since the solar wind interacts directly with the atmospheres and ionospheres of these planets. Venus and Mars are now known to be non-magnetic planets and in this paper a brief description of the ionosphere and atmosphere of Venus as evolved through several planetary missions, particularly the Pioneer Venus Orbiter which had onboard several aeronomy experiments, has been given. The results on the response of the Venus ionosphere and its upper atmosphere to changes in solar wind, especially on (i) disappearing atmospheres, (ii) orbit-to-orbit variability of electron and ion concentration and (iii) location of nightside ionopause are presented. These results in relation to features like plasma holes and disappearing ionospheres are also discussed