Modeling the Planetary Exospheres: Application to Earth and Titan

Abstract: The planetary coronae (or exospheres) are poorly known in their outer parts, since neutral
densities are low compared with the instruments detection capabilities. The exospheric models are thus often the main source of information at such high altitudes. We investigate here the importance of a specific exospheric population, i.e. satellite particles, which are usually neglected in the models. These particles are indeed produced through rare collisions in the exospheres, and may either be negligible or dominate the exospheres of all planets with dense atmospheres in our solar system, depending on their production and losses.

Here we present a numerical model for estimating the satellite particle density in the planetary exospheres, which is based on the rigorous calculation of the balance between the possible sources and losses of these particles in the outer layers of the atmosphere. As a first step, we applied this model to the Titan environment and to the outermost layers of the terrestrial atmosphere. We also discuss in detail the results of this modeling.