  The latest generation of high contrast instruments dedicated to exoplanets
and circumstellar disks imaging are equipped with extreme adaptive optics and
coronagraphs to reach contrasts of up to 10^--4 at a few tenths of arc-seconds
in the near infrared. The resulting image shows faint features, only revealed
with this combination, such as the wind driven halo. The wind driven halo is
due to the lag between the adaptive optics correction and the turbulence speed
over the telescope pupil. However we observe an asymmetry of this wind driven
halo that was not expected when the instrument was designed. In this letter, we
describe and demonstrate the physical origin of this asymmetry and support our
explanation by simulating the asymmetry with an end-to-end approach. From this
work, we found out that the observed asymmetry is explained by the interference
between the AO-lag error and scintillation effects, mainly originating from the
fast jet stream layer located at about 12 km in altitude. Now identified and
interpreted, this effect can be taken into account for further design of high
contrast imaging simulators, next generation or upgrade of high contrast
instruments, predictive control algorithms for adaptive optics or image
post-processing techniques.
