Morphology of the MRI in Axial Symmetry: existence of a magnetic threshold

Giovanni Montani, Daniela Pugliese

Published 2014-09-29Version 1

We analyze the linear stability of an axially symmetric ideal plasma disk, embedded in a magnetic field and endowed with a differential rotation. This study is performed by adopting the magnetic flux surface function as the fundamental dynamical variable, in order to outline the role played by the co-rotation theorem, in the background configuration. The present formulation shows the existence of a magnetic threshold for the emergence of a Magneto-rotational instability. In the Keplerian case, triggering unstable modes requires the magnetic field forms an angle greater than 30 degree with the equatorial plane.