Purely helical absolute equilibria and chirality of (magneto)fluid turbulence

TL;DR

This paper investigates the statistical equilibria of helical modes in (magneto)fluid turbulence, revealing how chiral sectors dominate and exploring cascade behaviors and dynamo processes across different fluid models.

Contribution

It introduces new insights into the chiral dominance in absolute equilibria and discusses novel cascade scenarios in various (magneto)fluid turbulence models.

Findings

Chiral sectors appear separately in absolute equilibria.

Dominance of one chiral sector influences turbulence states.

New cascade behaviors and dynamo mechanisms are proposed.

Abstract

Left- and right-handed helical modes' statistical absolute equilibria appear \textit{separately}. If both chiral sectors present, one can dominate around its positive pole, which is relevant to the nearly maximally helical (force free for magnetic field) states of turbulence. Pure magnetodynamics (PMD, or electron magnetohydrodynamics --- EMHD), pure hydrodynamics (PHD), and, single-fluid and two-fluid MHDs are studied. Relevant documented data and issues of cascade properties, and, helical and nonhelical dynamos are revisited. We also discuss new scenarios, such as PMD inverse magnetic helicity and forward energy cascades, and, the continuous transition from completely-inverse to partly-inverse-and-partly-forward and to completely-forward energy transfers in PHD.