The origins of $k^{-2}$ spectrum in the decaying Taylor-Green magnetohydrodynamic turbulent flows

TL;DR

This paper explores the origin of the $k^{-2}$ energy spectrum in decaying Taylor-Green magnetohydrodynamic turbulence, attributing it to magnetic discontinuities and current sheets rather than weak turbulence phenomenology.

Contribution

The study demonstrates that magnetic discontinuities and current sheets are responsible for the $k^{-2}$ spectrum in decaying MHD turbulence, challenging previous weak turbulence explanations.

Findings

Current sheets form at magnetic discontinuities.

Discontinuities influence the energy spectrum's $-2$ scaling.

Filtering techniques reveal the role of current sheets in spectral formation.

Abstract

We investigate the origins of $k^{-2}$ spectrum in a decaying Taylor-Green magnetohydrodynamic flow with zero large scale magnetic flux that was reported in Lee et al. (2010). A possible candidate for this scaling exponent has been the weak turbulence phenomenology. From our numerical simulations, we observe that current sheets in the magnetic Taylor-Green flow are formed in regions of magnetic discontinuities. Based on this observation and by studying the influence of the current sheets on the energy spectrum, using a filtering technique, we argue that the discontinuities are responsible for the $-2$ power law scaling of the energy spectra of this flow.