# The contribution of kinetic helicity to turbulent magnetic diffusivity

## TL;DR

This paper demonstrates through simulations that kinetic helicity introduces a significant negative quadratic contribution to turbulent magnetic diffusivity at high magnetic Reynolds numbers, affecting magnetic field evolution models.

## Contribution

It reveals a previously unanticipated quadratic negative effect of kinetic helicity on turbulent magnetic diffusivity at high magnetic Reynolds numbers.

## Key findings

- Turbulent magnetic diffusivity decreases with increasing kinetic helicity.
- At high magnetic Reynolds numbers, helicity reduces diffusivity by about half.
- The negative quadratic contribution becomes significant beyond the quasilinear regime.

## Abstract

Using numerical simulations of forced turbulence, it is shown that for magnetic Reynolds numbers larger than unity, i.e., beyond the regime of quasilinear theory, the turbulent magnetic diffusivity attains an additional negative contribution that is quadratic in the kinetic helicity. In particular, for large magnetic Reynolds numbers, the turbulent magnetic diffusivity without helicity is about twice the value with helicity. Such a contribution was not previously anticipated, but, as we discuss, it turns out to be important when accurate estimates of the turbulent magnetic diffusivity are needed.