Magnetic, Kinetic, and Transition Regime: Spatially-Segregated Structure of Compressive MHD Turbulence

Turbulence is a complex physical process prevalent in modern physics, particularly in ionized environments like interstellar gas, where magnetic fields play a dynamic role. However, the precise influence of magnetic fields in such settings remains unclear. We employ the Alfvén Mach number, $M_{\mathrm{A}}=\sqrt{E_{\mathrm{k}}\mathrm{/}{E}_{\mathrm{B}}}$, to gauge the magnetic field’s significance relative to turbulent motion, uncovering diverse interaction patterns. In the low-$M_{\mathrm{A}}$ magnetic regime, the field is force-free, yet gas motion does not align with it. At intermediate $M_{\mathrm{A}}$ (magnetic-kinetic transition regime), velocity and magnetic fields show peak alignment, likely due to rapid relaxation. In the high-$M_{\mathrm{A}}$ kinetic regime, both fields are irregular and unaligned. These regimes find observational counterparts in interstellar gas, highlighting the multifaceted nature of MHD turbulence and aiding future astrophysical interpretations.