A Comparative Study of Turbulence Statistics in the ISM Driven by Fourier-Space Forcing and Expanding Bubbles

Abstract

Past studies of turbulence in the Interstellar Medium (ISM) have simulated turbulent sources through the Fourier space driving (FSD). These studies have demonstrated that the resulting statistical distributions of the fluid are highly sensitive to the exact driving form, highlighting a need to analyze which form reproduces which aspects of the ISM. Real observations have shown regions of expanding bubbles commonly sourced by supernovae dominate the dynamic structure. This local source of turbulence is largely different from the global scale FSD method. To find regions in the FSD method that best reproduce the statistical distributions created by expanding bubbles, we compare both distributions outputted from MHD simulations. We utilized AthenaK, to which we’ve added a momentum bubble injection method. Our results show no FSD model is able to reproduce the resulting distributions of the momentum injection method. The velocity distributions are largely different between the two methods, with the momentum injection method generating larger power in the velocity field than all tested FSD models. We did find that both the purely compressive and momentum injection methods produce density distributions that are not log-normal. The momentum injection method possibly fits the log-normal distribution well largely, only deviating in low density non- Gaussian portions.