The Role of Superthermal Electrons on the Escaping Ions From the Upper Atmosphere of Titan and Venus

Abstract

The observed escape of ions from the ionosphere of planets and moons is of interest during the last few years. Different mechanisms that can explain the escape of charged particles were assumed. One of the recent mechanisms to explain the ionospheric loss is the plasma expansion approach. In the present work, we investigate the ionic loss from the moon Titan and planet Venus, where their ionospheres suffer from a continues loss reaches to several tons of ions per day. For this purpose, we use a suitable set of hydrodynamic fluid equations to describe the plasma system in either Titan or Venus. Interestingly, it is observed that superthermal electrons are exist in both cases (i.e. Titan and Venus ionosphere). The selfsimilar transformation is used to reduce the basic equations to ordinary differential equations which can be solved numerically to obtain the profiles of the plasma ion density, velocity, and potential during the expansion interval. Furthermore, it is of interest to examine the role of the superthermal electrons on the expansion profile properties.