  Deviations from axial symmetry are necessary to maintain self-sustained
MRI-turbulence. We define the parameters region where nonaxisymmetric MRI is
excited and study dependence of the unstable modes structure and growth rates
on the relevant parameters. We solve numerically the linear eigenvalue problem
for global axisymmetric and nonaxisymmetric modes of standard-MRI in Keplerian
disks with finite diffusion. For small magnetic Prandtl number the microscopic
viscosity completely drops out from the analysis so that the stability maps and
the growth rates expressed in terms of the magnetic Reynolds number Rm and the
Lundquist number S do not depend on the magnetic Prandtl number Pm. The minimum
magnetic field for onset of nonaxisymmetric MRI grows with Rm. For given S all
nonaxisymmetric modes disappear for sufficiently high Rm. This behavior is a
consequence of the radial fine-structure of the nonaxisymmetric modes resulting
from the winding effect of differential rotation. It is this fine-structure
which presents severe resolution problems for the numerical simulation of MRI
at large Rm. For weak supercritical magnetic fields only axisymmetric modes are
unstable. Nonaxisymmetric modes need stronger fields and not too fast rotation.
If Pm is small its real value does not play any role in MRI.
