A wavelike origin for clumpy structure and broad line wings in molecular clouds

The strong magnetosonic waves that are likely to be generated by virialized motions in molecular clouds should steepen into shocks and density irregularities that may be identified with some of the fine-scale or clumpy structure in these clouds. This process is illustrated here with a numerical solution to the magnetosonic equations with diffusion, in the case of two colliding, linearly polarized wavetrains. The parallel and perpendicular velocities that are associated with such clumps are comparable to the local Alfven speed. This implies that the broad wings in non-Gaussian line profiles (unassociated with embedded stars) could be the result of wave-related motions in the low-density regions of molecular clouds. Theoretical composite line profiles derived for a line of sight containing density substructures of the form n proportional to r exp -alpha and Alfven velocity variations of the form vA proportional to n exp -beta fit the observed core-wing molecular line profiles for reasonable alpha and beta.