Instability of the Stochastic Galactic Magnetic Field

Abstract

We examine the e †ects of the stochastic galactic magnetic Ðeld on the dynamical instability of the interstellar gas and magnetic Ðeld. The large-scale random walk, or meandering, of the magnetic Ðeld exerts stresses across the average magnetic Ðeld direction, which suppress the growth of perturbations having a small wavelength normal to the Ðeld. The result is that, compared with a nonstochastic initial magnetic Ðeld, those perturbations, which grow, are signiÐcantly broadened in the direction normal to the Ðeld. Hence, the instability in a stochastic magnetic Ðeld, 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 Ðeld.