  We analyze the stability of a thin plasma disk which is rotating around a
compact astrophysical object and is embedded in the strong magnetic field of
such a source. The aim of this study is the determination of a new type of
unstable modes, able to replace the magneto-rotational instability profile for
low beta-values and for sufficiently small scales of the perturbations, where
it fails. In particular, we consider the magneto-hydrodynamical scheme
including a non-zero Nernst coefficient, corresponding to first-order
collisional effects. As a result, modes with imaginary frequency lead to an
instability regime when the magnetic tension vanishes. Finally, we show that,
even in the presence of resistive effects, it remains a good candidate to
ensure the onset of a turbulent behavior in the absence of the
magneto-rotational instability.
