Scaling laws and diffuse locality of balanced and imbalanced MHD turbulence

TL;DR

This paper investigates the behavior of magnetohydrodynamic turbulence with energy imbalance, showing that in low-imbalance limits the turbulence aligns with the balanced Goldreich-Sridhar model, challenging the Perez-Boldyrev model.

Contribution

The study provides high-resolution simulations demonstrating the transition from imbalanced to balanced MHD turbulence and critiques existing models based on numerical evidence.

Findings

Low-imbalance MHD turbulence aligns with the Goldreich-Sridhar model.

Perez-Boldyrev model's prediction of equal nonlinear timescales is contradicted.

Numerical simulations challenge existing theories of imbalanced turbulence.

Abstract

The search of ways to generalize the theory of strong MHD turbulence for the case of non-zero cross-helicity (or energy imbalance) has attracted considerable interest recently. In our earlier publications we performed three-dimensional numerical simulations and showed that some of existing models are inconsistent with numerics. In this paper we focused our attention on low-imbalance limit and performed new high-resolution simulations. The results strongly suggest that in the limit of small imbalances we smoothly transition to a standard Goldreich-Sridhar (1995) balanced model. We also claim that Perez-Boldyrev (2009) model that predicts the same nonlinear timescale for both components due to so-called "dynamic alignment" strongly contradicts numerical evidence.