Effects of Turbulence Driving and Sonic Mach Number on the Davis–Chandrasekhar–Fermi Method

Abstract

The Davis–Chandrasekhar–Fermi (DCF) method is a tool that is widely used to obtain the strength of the mean magnetic field projected on the plane of the sky. However, it may overestimate the strength of the magnetic field when there are many independent structures (or, eddies) along the line of sight. Recently, Cho & Yoo proposed a modified DCF method that corrects such an effect. In this paper, we compare the conventional DCF method and the modified DCF method for various sonic Mach numbers and driving schemes. We find that, when we apply the conventional DCF method to turbulence generated by solenoidal and compressive driving schemes, the results are notably different. In particular, when there are many independent eddies along the line of sight, the estimates of the plane-of-sky mean magnetic field for compressive driving show strong dependence on the sonic Mach number, while those for solenoidal driving exhibit a very weak dependence on it. We find that intermittency of magnetic and density structures is responsible for the sonic Mach number dependence of the conventional DCF method. On the other hand, the modified DCF does not show strong dependence on the sonic Mach number or the driving scheme.