  We present two-dimensional multi-fluid numerical modelling of the upper
atmosphere of the hot Jupiter WASP-12b. The model includes hydrogen chemistry,
and self-consistently describes the expansion of the planetary upper atmosphere
and mass loss due to intensive stellar irradiation, assuming a weakly
magnetized planet. We simulate the planetary upper atmosphere and its
interaction with the stellar wind (SW) with and without the inclusion of tidal
force and consider different XUV irradiation conditions and SW parameters. With
the inclusion of tidal force, even for a fast SW, the escaping planetary
material forms two streams, propagating towards and away from the star. The
atmospheric escape and related mass loss rate reaching the value of 10^12 gs^-1
appear to be mostly controlled by the stellar gravitational pull. We computed
the column density and dynamics of MgII ions considering three different sets
of SW parameters and XUV fluxes. The simulations enable to compute the
absorption at the position of the Mg h line and to reproduce the times of
ingress and egress. In case of a slow SW and without accounting for tidal
force, the high orbital velocity leads to the formation of a shock
approximately in the direction of the planetary orbital motion. In this case,
mass loss is proportional to the stellar XUV flux. At the same time, ignoring
of tidal effects for WASP-12b is a strong simplification, so the scenario with
a shock, altogether is an unrealistic one.

Earth and Planetary Astrophysics