  We present the first realistic 3D simulations of flame front instabilities
during type I X-ray bursts. The unperturbed front is characterised by the
balance between the pressure gradient and the Coriolis force of a spinning
neutron star ({\nu} = 450 Hz in our case). This balance leads to a fast
horizontal velocity field parallel to the flame front. This flow is strongly
sheared in the vertical direction. When we perturb the front an instability
quickly corrugates the front. We identify this instability as the baroclinic
instability. Most importantly, the flame is not disrupted by the instability
and there are two major consequences: the overall flame propagation speed is
{\sim} 10 times faster than in the unperturbed case and distinct flame vortices
appear. The speedup is due to the corrugation of the front and the dynamics of
the vortices. These vortices may also be linked to the oscillations observed in
the lightcurves of the bursts.

High Energy Astrophysical Phenomena