Magneto-viscous effects on the ideal and resistive gravitational instabilities in Cartesian theory

The leading terms of an expansion using large parameter omega c tau ( omega c=cyclotron frequency, tau =collision time) from a recent closed form for the non-hydrostatic part of the stress tensor are identified as the 'parallel', FLR and 'perpendicular' components, respectively. With the appropriate contributions to the ion stress, all the relevant results existing in the literature concerning the potential stabilization of the ideal and resistive gravitational instabilities of stratified plasma follow. A new result given is that the weakly localized resistive-g instability of stratified plasma in a uniform magnetic field is slowed down due to the ion 'perpendicular' viscosity at lower temperatures, but is essentially unmodified at higher temperatures. Finally, it is noted that the 'parallel' viscosity is quite unimportant in the present Cartesian theory, and that a proper treatment of the influence of magnetic field curvature may well be needed.