Multi-scale Pressure-balanced Structures in Three-dimensional Magnetohydrodynamic Turbulence

TL;DR

This paper uses numerical simulations to explore the formation of multi-scale pressure-balanced structures in three-dimensional compressible magnetohydrodynamic turbulence, revealing their association with slow-mode waves and their spectral properties.

Contribution

It demonstrates the existence of multi-scale PBSs in 3D MHD turbulence and links their formation to oblique slow-mode waves through high-resolution simulations.

Findings

Magnetic and thermal pressures follow a Kolmogorov-like spectrum.

Multi-scale PBSs are embedded within larger structures.

PBSs are associated with oblique slow-mode waves.

Abstract

Observations of solar wind turbulence indicate the existence of multi-scale pressure-balanced structures (PBSs) in the solar wind. In this work, we conduct a numerical simulation to investigate multi-scale PBSs and in particular their formation in compressive MHD turbulence. By the use of a higher order Godunov code Athena,a driven compressible turbulence with an imposed uniform guide field is simulated. The simulation results show that both the magnetic pressure and the thermal pressure exhibit a turbulent spectrum with a Kolmogorov-like power law, and that in many regions of the simulation domain they are anti-correlated. The computed wavelet cross-coherence spectrum of the magnetic pressure and the thermal pressure, as well as their space series, indicate the existence of multi-scale PBSs, with the small PBSs being embedded in the large ones. These multi-scale PBSs are likely to be related with the highly oblique-propagating slow-mode waves, as the traced multi-scale PBS is found to be traveling in a certain direction at a speed consistent with that predicted theoretically for a slow-mode wave propagating in the same direction.