Numerical Magnetohydrodynamic Studies of Turbulence and Star Formation

Summary

In this paper we examine two problems numerically. The first problem concerns the structure and evolution of MHD turbulence. Simulations are presented which show evidence of forming a turbulent cascade leading to a self-similar phase and eventually a decay phase. Several dynamical diagnostics of interest are tracked. Spectra for the kinetic and magnetic energies are presented. The second problem consists of the formation of pre-protostellar cores in a turbulent, magnetized molecular clouds. It is shown that the magnetic field strength correlates positively with the density in keeping with observations. It is also shown that the density and magnetic fields organize themselves into filamentary structures. Through the construction of simulated channel maps it is shown that accretion onto the cores takes place along the filaments. Thus a new dynamical process is reported for accretion onto cores. We have used the first author's RIEMANN code for astrophysical fluid dynamics for all these calculations.

Introduction

The conference for which this paper is being written has been instrumental in opening the eyes of astronomers to the need for understanding turbulent processes in astrophysics. While several astrophysical environments where turbulent processes could be important were identified by numerous contributors in this conference, the pulsar scintillation measurements and the study of lines in molecular clouds provide two environments where the need for magnetohydrodynamic (MHD) turbulence is observationally well-founded. Since the MHD equations are highly non-linear analytical approaches sometimes prove to be of limited utility.