Dynamics of planetary ions in the induced magnetospheres of Venus and Mars

We compare dynamics of planetary ions in the induced magnetospheres of Venus and Mars in a global hybrid simulation to study factors controlling the ion escape at unmagnetized planets. In the simulation we find that the finite Larmor radius (FLR) effects of escaping heavy ions are stronger at Mars than Venus under nominal solar wind conditions. But, varying upstream conditions, especially the IMF, affects the strength of the FLR effects. We classify three basic types of planetary ion dynamics in an induced magnetosphere. First, light ions such as hydrogen follow the E x B drift, and escape in the wake in the hemisphere where the solar wind convection electric field is pointing towards the planet. Second, heavy ions like oxygen undergo FLR effects, and escape mainly outside of the wake in the hemisphere where the solar wind convection electric field is pointing away from the planet. Third, ion species between light and heavy ions can have both the E x B and FLR type dynamics in the same time. (C) 2015 Elsevier Ltd. All rights reserved.