Projected surface density of the planetary wind as seen by the observer. The planet moves from left to right, with the leading stream being observed during negative orbital phases. The red circle represents the angular size of the planet and the white circle the angular size of the stellar disk, and thus the gas probed during mid-transit. In the leading stream, at phase -0.03, the gas converges and flares out again. In this high-density region, the gas is moving away from the observer, resulting in a redshifted spectral feature.