MODEL OF SUPERTHERMAL IONS IN THE VENUS IONOSPHERE

A model is presented that simulates the behavior of superthermal ions previously reported in the dayside ionosphere of Venus. The model considers effects of ExB and gradient drifts, charge exchange and collisions with the ambient neutral atmosphere and the possible effects of a wave-particle (anomalous) scattering process. Results indicate that scattering processes are required if superthermal ions are the explanation for the observed ''missing pressure'' component in the day-side Venus ionosphere. The scattering scale length required to match the ''missing pressure'' distribution is similar to the scale length previously predicted for growth of a lower hybrid beam instability.