On the magnetic quenching of mean-field effects in supersonic interstellar turbulence

TL;DR

This paper investigates how large-scale magnetic fields in the interstellar medium are affected by turbulent dynamo processes, especially focusing on the quenching of mean-field effects in supersonic turbulence, extending analysis into regimes with significant magnetic fields.

Contribution

It extends the analysis of turbulent transport coefficients into the nonlinear regime, deriving quenching functions for key dynamo effects in supersonic interstellar turbulence.

Findings

Quenching functions for the alpha effect, diamagnetic pumping, and turbulent diffusivity were derived.

Suppression of vertical wind at late times impacts magnetic helicity removal.

Results suggest late-stage effects could challenge mean-field dynamo models.

Abstract

The emergence of large-scale magnetic fields observed in the diffuse interstellar medium is explained by a turbulent dynamo. The underlying transport coefficients have previously been extracted from numerical simulations. So far, this was restricted to the kinematic regime, but we aim to extend our analysis into the realm of dynamically important fields. This marks an important step on which derived mean-field models rely to explain observed equipartition strength fields. As in previous work, we diagnose turbulent transport coefficients by means of the test-field method. We derive quenching functions for the dynamo {\alpha} effect, diamagnetic pumping, and turbulent diffusivity, which are compared with theoretical expectations. At late times, we observe the suppression of the vertical wind. Because this potentially affects the removal of small-scale magnetic helicity, new concerns arise about circumventing constraints imposed by the conservation of magnetic helicity at high magnetic Reynolds numbers. While present results cannot safely rule out this possibility, the issue only becomes important at late stages and is absent when the dynamo is quenched by the wind itself.