Asymmetry in the Jovian auroral Lyman-α line profile due to thermospheric high-speed flow

The presence of a fast wind in the auroral region atmosphere of Jupiter has been detected from the Doppler shift in near-IR observations of H-3(+) emissions. The Doppler effect also modifies auroral resonance emission line shapes. We present a new radiative transfer equation for the hydrogen Lyman-alpha line in the presence of a horizontal wind and solve it numerically using the Feautrier method. This model allows us to derive the theoretical profile of the Lyman-alpha emission line. We apply this code to long slit echelle spectra of Jupiter's auroral Lyman-alpha emission obtained by HST-STIS which exhibit a self-reversed and asymmetric profile. Using a simple expression for the vertical variation of the horizontal wind velocity, we find the HST-STIS observations are well reproduced by a velocity profile reaching similar to 4-8 km/s near similar to 10(-5) mu bar pressure altitude (similar to 1500 km above the 1 bar level). The velocity is much higher than velocity derived from H-3(+) emission peaking at similar to 550 km and consistent with an increase of the velocity with regards to altitude but reaching larger values than predicted by circulation models at similar to 10(-5) mu bar.