Global hybrid simulations of solar wind interaction with Mercury: Magnetosperic boundaries

The Mariner 10 observations established the presence of a magnetosphere at Mercury with general characteristics similar to that of the Earth despite a much smaller size (i.e., magnetic dipole strength) and the absence of an atmosphere-ionosphere. Observationally, a mapping between the terrestrial and hermean magnetospheric regions has been made which entails increasing the size of the planet by a factor of 8. Recently, we have used the results of global hybrid (kinetic ions, fluid electrons) simulations of solar wind interaction with magnetic dipoles of varying strength to show the existence of a spectrum of magnetospheric structures whose size and level of complexity increases with the dipole moment. A physical parameter which helps characterize these magnetospheres is Dp, the distance ahead of the dipole where the magnetic field pressure balances the solar wind dynamic pressure. Expressed in units of ion skin depth, when Dp ∼ > 20 the interaction results in the formation of an earthlike magnetosphere. Thus, the magnetosphere of Mercury with Dp ∼ 65 should resemble that of the Earth. However, not all magnetospheric processes in Dp > 20 magnetospheres are guaranteed to be alike and possess the same spatial and temporal scales. In this paper, we use the results of global hybrid simulations, corresponding to Dp = 64, to examine the nature of the boundaries and discontinuities at the hermean magnetosphere and how they compare with the corresponding regions at the Earth.