  We examine the linear stability of a filamentary cloud permeated by a
perpendicular magnetic field. The initial magnetic field is assumed to be
uniform and perpendicular to the cloud axis. The model cloud is assumed to have
a Plummer-like density profile and to be supported against the self-gravity by
turbulence. The effects of turbulence are taken into account by enhancing the
effective pressure of a low density gas. We derive the effective pressure as a
function of the density from the condition of the hydrostatic balance. It is
shown that the model cloud is more unstable against radial collapse, when the
radial density slope is shallower. When the magnetic field is mildly strong,
the radial collapse is suppressed. If the displacement vanishes in the region
very far from the cloud axis, the model cloud is stabilized completely by a
mildly strong magnetic field. If rearrangement of the magnetic flux tubes is
permitted, the model cloud is unstable even when the magnetic field is
extremely strong. The stability depends on the outer boundary condition as in
case of the isothermal cloud. The growth rate of the rearrangement mode is
smaller when the radial density slope is shallower.

Astrophysics of Galaxies