  In dilute astrophysical plasmas, the collisional mean free path of a particle
can exceed its Larmor radius. Under these conditions, the thermal conductivity
and viscosity of the plasma can be dramatically altered. This alteration allows
outwardly decreasing angular velocity or temperature gradients to become
strongly destabilizing. This paper generalizes an earlier, simple analysis of
the viscosity instability, by including the dynamical effects of magnetic field
line tension. Such effects lower the growth rates found in the absence of such
tension, but still allow growth rates in excess of the maximum of the standard
magnetorotational instability. We find very good quantitative agreement with
more complex kinetic treatments of the same process. The combination of large
growth rates and large magnetic Prandtl number suggest that protogalactic disks
are powerful dynamos.
