Magnetic filamentary structures in the ${\alpha}^{2}$ dynamo spectrum in plasmas

TL;DR

This paper explores the role of filamentary structures in the ${ m oldsymbol{ extalpha}}^{2}$ dynamo spectrum within plasmas, highlighting the influence of curvature, diffusion, and filament thickness on dynamo behavior in 2D and 3D media.

Contribution

It introduces a filamentary Frenet frame approach to analyze kinematic chaotic dynamos in 3D Euclidean space, simplifying curvature considerations to a single scalar curvature parameter.

Findings

Filamentary structures are crucial in the ${ m oldsymbol{ extalpha}}^{2}$ dynamo spectrum.

Dynamo action is absent or slow in 2D, consistent with Cowling's theorem.

Filament thickness correlates with scalar curvature, affecting dynamo properties.

Abstract

Kinney et al [PPL \textbf{1},(1994)] have investigated plasma filamentary structure dynamics. More recently, Wilkin et al [Phys Rev Lett \textbf{99}:134501,(2007)] have shown that kinetic energy spectrum of magnetic structures in small-scale dynamos, are predominantly filamentary. Kirilov et al [PRE (2009)] have shown that use of the boundary values of the mean-field isotropic helical turbulent ${\alpha}^{2}$-dynamo, could determine the morphology of dynamo instability. In this paper, filamentary Frenet frame in diffusive media, displays the existence of kinematic chaotic dynamo in 3D Euclidean space ${\textbf{E}^{3}}$. In 2D, either no dynamo action spectrum is found, in agreement with Cowling anti-dynamo theorem, or slow dynamos [PPL \textbf{15},(2008)]. Curvature and diffusion effects are encodded in the matrix representation of ${\alpha}^{2}$-dynamo operator. Instead of principal scalar curvatures ${\kappa}_{1}$ and ${\kappa}_{2}$ of the surface of structures, only one scalar curvature ${\kappa}$ is needed to determine dynamos spectra. Filament thickness, increases with scalar curvature, as happens in solar physics.