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

TL;DR

This paper investigates the structure of compressive MHD turbulence across different magnetic regimes, revealing how magnetic and kinetic energies influence field alignment and turbulence characteristics in astrophysical environments.

Contribution

It introduces a framework using the Alfvén Mach number to categorize turbulence regimes and describes their distinct magnetic and velocity field behaviors.

Findings

Low-${M}_{A}$ regime: force-free magnetic fields with unaligned gas motion.

Intermediate-${M}_{A}$ regime: peak alignment of magnetic and velocity fields.

High-${M}_{A}$ regime: irregular, unaligned magnetic and velocity fields.

Abstract

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 Alfv\'{e}n Mach number, ${M}_{\mathrm{A}} = \sqrt{E_{\mathrm{k}}/E_{\mathrm{B}}}$, 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.