http://arxiv.org/abs/2201.05620
We study the magnetic field to density ($B-\rho$) relation in turbulent molecular clouds with dynamically important magnetic fields using nonideal three-dimensional magnetohydrodynamic simulations. Our simulations show that there is a distinguishable break density $\rho_{\rm T}$ between the relatively flat low density regime and a power-law regime at higher densities. We present an analytic theory for $\rho_{\rm T}$ based on the interplay of the magnetic field, turbulence, and gravity. The break density $\rho_{\rm T}$ scales with the strength of the initial Alfv\’en Mach number $\mathcal{M}{\rm A0}$ for sub-Alfv\’enic ( $\mathcal{M}{\rm A0}<1$) and trans-Alfv\’enic ($\mathcal{M}{\rm A0} \sim 1$) clouds. We fit the variation of $\rho{\rm T}$ for model clouds as a function of $\mathcal{M}{\rm A0}$, set by different values of initial sonic Mach number $\mathcal{M{\rm 0}}$ and the initial ratio of gas pressure to magnetic pressure $\beta_{\rm 0}$. This implies that $\rho_{\rm T}$, which denotes the transition in mass-to-flux ratio from the subcritical to supercritical regime, is set by the initial turbulent compression of the molecular cloud.
S. Auddy, S. Basu and T. Kudoh
Wed, 19 Jan 22
53/121
Comments: 6 Pages, 3 Figures, submitted to ApJL