Anchoring Magnetic Field in Turbulent Molecular Clouds

TL;DR

This paper investigates the role of magnetic fields in star formation by analyzing their orientation across different scales in molecular clouds, finding that sub-Alfvenic turbulence best explains observed magnetic field alignments.

Contribution

It introduces a method to connect magnetic field orientations from large to small scales and compares observations with simulations to identify the turbulence regime.

Findings

Significant correlation in magnetic field orientations across scales.

Sub-Alfvenic turbulence matches observed magnetic field alignments.

Supports the importance of magnetic fields in star formation processes.

Abstract

One of the key problems in star formation research is to determine the role of magnetic fields. Starting from the atomic inter-cloud medium (ICM) which has density nH ~ 1 per cubic cm, gas must accumulate from a volume several hundred pc across in order to form a typical molecular cloud. Star formation usually occurs in cloud cores, which have linear sizes below 1 pc and densities nH2 > 10^5 per cubic cm. With current technologies, it is hard to probe magnetic fields at scales lying between the accumulation length and the size of cloud cores, a range corresponds to many levels of turbulent eddy cascade, and many orders of magnitude of density amplification. For field directions detected from the two extremes, however, we show here that a significant correlation is found. Comparing this result with molecular cloud simulations, only the sub-Alfvenic cases result in field orientations consistent with our observations.