Dynamics of the Magnetoviscous Instability

In dilute astrophysical plasmas, the collisional mean free path of a particlecan exceed its Larmor radius. Under these conditions, the thermal conductivityand viscosity of the plasma can be dramatically altered. This alteration allowsoutwardly decreasing angular velocity or temperature gradients to becomestrongly destabilizing. This paper generalizes an earlier, simple analysis ofthe viscosity instability, by including the dynamical effects of magnetic fieldline tension. Such effects lower the growth rates found in the absence of suchtension, but still allow growth rates in excess of the maximum of the standardmagnetorotational instability. We find very good quantitative agreement withmore complex kinetic treatments of the same process. The combination of largegrowth rates and large magnetic Prandtl number suggest that protogalactic disksare powerful dynamos.Comment: 7 pages, 4 figure