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Simulation results are presented for the Lyα flux impact from the parent star on the Hα absorption spectrum in the atmospheres of the hot Jupiters HD189733b and HD 209458b. The atmosphere is simulated using a three-dimensional hydrodynamic code. Several options are considered for the upper atmospheric composition, including variations in the XUV parameter. The Lyα photon transfer in the atmosphere is simulated by the Monte Carlo method. Spatial distributions are obtained for the bulk density of hydrogen atoms excited to the second energy level; absorption spectra in the Hα line are calculated. It is shown that the transit absorption of the hot Jupiters in the Hα line can be described by a relatively simple model of the Lyα photon transfer in the upper atmosphere. [ABSTRACT FROM AUTHOR]

We present two-dimensional multifluid 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 1012 g s−1 appear to be mostly controlled by the stellar gravitational pull. We computed the column density and dynamics of Mg  ii 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. [ABSTRACT FROM AUTHOR]