Instability of the stochastic galactic magnetic field

We examine the effects of the stochastic galactic magnetic field on the dyn amical instability of the interstellar gas and magnetic held. The large-sca le random walk, or meandering, of the magnetic held exerts stresses across the average magnetic held direction, which suppress the growth of perturbat ions having a small wavelength normal to the held. The result is that, comp ared with a nonstochastic initial magnetic held, those perturbations, which grow, are significantly broadened in the direction normal to the held. Hen ce, the instability in a stochastic magnetic held, such as that observed in our Galaxy, should evolve into clouds that are more similar to those that are observed than are those found in the absence of the stochastic field.