## On the global stability of rotating magnetized disks
Global modes of the magnetic shear instability in horizontally
unbounded rotating disks are studied by solving the linear eigenvalue
problem. Nonaxisymmetry and finite diffusivities are allowed for. The
instability exists in a range of the magnetic field amplitudes between
the minimum value, , imposed by the finite
diffusivities and the maximum amplitude, ,
brought about by the finite thickness of the disk. The unstable modes
for the magnetic field close to the lower and upper bounds occupy
different regions in the disk. The critical rotation rates for onset
of the instability for the excitations with various axial and vertical
symmetries are estimated and their dependencies on the external
magnetic field amplitude are defined. The axisymmetric modes with
symmetric magnetic field and antisymmetric velocity relative to the
disk mid-plane are most easily excited. The effective diffusivity
produced by the supernova explosions is small enough for the
instability to be active in the galactic disk. The possibility of the
## Contents© European Southern Observatory (ESO) 1997 Online publication: May 26, 1998 |