Thermomagnetic instability of a rotating magnetized plasma disc

We analyse the stability of a thin plasma disc 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 newtype of unstable modes, able to replace the magnetorotational instability profile for low-ß values and for sufficiently small scales of the perturbations, where it fails. In particular, we consider the magnetohydrodynamical 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 behaviour in the absence of the magnetorotational instability. © 2013 The Authors Published by Oxford University Press on behalf of the Royal Astronomical Society.