Interaction of Herbig-Haro objects with molecular cloud and generation of Alfvén waves

Abstract

The interaction of a jet with the surrounding molecular cloud can be a mechanism for turbulence generation. In this paper we present the results of two-dimensional, Cartesian, isothermal magnetohydrodynamics simulations of high-density clumps (which could be the result of a time-dependent ejection from a young, low-mass star) propagating in a uniform medium. We also study the generation of Alfvén waves and the transfer of momentum and energy from the clump to the molecular cloud. We calculate the time and the distances in which the momentum and the energy of the clump are transferred to the molecular cloud, for models with different magnetic field configurations. We find that the presence of the magnetic field facilitates the transport of momentum and energy by the propagation of Alfvén waves in the direction perpendicular to the jet motion; in this way, jets can generate turbulence in the surrounding, magnetized cloud. We also find that jets moving parallel to the ambient magnetic field travel much longer distances than jets moving perpendicular to the magnetic field. This effect could explain the correlation between the direction of the magnetic field and the directions of the outflows embedded in molecular clouds. © 2005 RAS.