Views of GJ 436 b exosphere (dots) within the orbital plane, seen from the top, at the time of the optical transit. The two panels correspond to two simulations performed with the same escape rate, planetary wind velocity, and photoionization rate, but without stellar wind interactions (left panel) or including them (right panel, corresponding to the best fit for Visit 2). The planet is represented by a small black disk, to scale, between the dashed black lines limiting the LOS toward the stellar disk. Arrows display the average velocity field of the neutral hydrogen atoms in the stellar rest frame, with particles colored as a function of the time they escaped the atmosphere (for planetary neutrals) or were created through charge exchange (for neutralized protons). With no stellar wind interactions the dynamics of the escaping gas is initially dominated by the planetary orbital velocity and later constrained by radiative braking. With charge exchange most protons are neutralized in the dense inner coma, abrading at the source planetary neutrals that would have fed the outer regions of the exosphere, but also creating a compact population of neutrals dominated by the radial bulk velocity of the stellar wind. It takes much more time for stellar gravity to eventually disperse this population of neutralized protons.