Nonlocal Contributions to the Turbulent Cascade in Magnetohydrodynamic Turbulence

TL;DR

This paper investigates nonlocal effects in MHD turbulence energy transfer, proposing an additional term to the classical law, supported by simulations, which impacts understanding of solar wind heating.

Contribution

It introduces a nonlocal transfer term to the MHD turbulence energy cascade law, enhancing the understanding of energy dissipation in plasma turbulence.

Findings

Nonlocal transfer term affects energy dissipation estimates.

Neglecting nonlocal effects can overestimate dissipation rates.

Implications for solar wind heating models.

Abstract

We present evidence for nonlocal contributions to the turbulent energy cascade in magnetohydrodynamic (MHD) plasmas. Therefore, we revisit a well-known result derived directly from the MHD equations, i.e., the Politano and Pouquet (P&P) law for the transfer of kinetic and magnetic energy in scale. We propose adding a term that accounts for nonlocal transfer and represents the influence of fluctuations from large scales due to the Alfv\'en effect. Supported by direct numerical simulations of homogeneous and isotropic MHD turbulence, we verify that in some plasma configurations, neglecting the additional nonlocal term might consistently overestimate energy dissipation rates and, thus, the contributions of turbulent energy dissipation potentially affecting solar wind heating; a central puzzle in space plasma physics that motivates the present work.