Fragmentation in collapsing magnetic gas clouds - Non-uniform initial fields

It is hypothesized that stars form by means of a mechanism that allows a collapsing interstellar cloud to fragment into a number of collapsing stellar-sized subcondensations. Defining the critical mass of a cloud as the mass a cloud must exceed in order for its gravitational force to overcome the resistive thermal, rotational and magnetic forces, it is proposed that the galactic magnetic field causes the critical mass to decrease as the cloud collapses down the field lines. To test this conjecture, the fully three-dimensional equations of magnetohydrodynamics were solved using an extension of the numerical method SPH. A selection of four initially nonuniform fields was examined, and results of numerical simulations are given. It is concluded that the level of uniformity of the initial field is not a significant factor in the context of this study, and that the effect of the magnetic field is to resist density increases while simultaneously allowing the material to flow down the field lines. As a result of this downward flow, the collapse becomes dominated by gravity and the cloud collapses into a thin disc. In addition to magnetic force, pressure also serves as a density-reducing variable.