  The magnetosphere of Mercury is studied using an implicit full particle in
cell simulation (PIC). We use a hybrid simulation where ions are full particles
and electrons are considered as a fluid to start a full PIC simulation where
electrons are also particles and follow their distribution function. This
approach allows us to estimate the changes introduced by the electron kinetic
physics. We find that the overall macroscopic state of the magnetosphere of
Mercury is little affected but several physical processes are significantly
modified in the full PIC simulation: the foreshock region is more active with
more intense shock reformation, the Kelvin-Helmholtz rippling effects on the
nightside magnetopause are sharper, and the magnetotail current sheet becomes
thinner than those predicted by the hybrid simulation. The greatest effect of
the electron physics, comes from the processes of particle energization. Both
species, not just the electrons, are found to gain more energy when kinetic
electron processes are taken into account. The region with the most energetic
plasma is found on the dusk side of the tail where magnetic flux ropes are
formed due to reconnection. We find that the ion and electron energization is
associated with the regions of reconnection and the development of kinetic
instabilities caused by counter-streaming electron populations. The resulting
electron distributions are highly non Maxwellian, a process that neither MHD
nor hybrid models can describe.
