Non-Gaussian generalization of the Kazantsev-Kraichnan model

TL;DR

This paper extends the Kazantsev-Kraichnan model to include statistical time asymmetry, enabling the study of velocity fields with energy cascade and analyzing magnetic field growth in turbulent dynamos.

Contribution

It introduces a generalized Kazantsev equation accounting for flow time asymmetry and investigates magnetic field evolution at large magnetic Prandtl numbers.

Findings

Magnetic field growth rate approaches the T-exponential limit as Pr_m increases.

Magnetic field generation is weaker than in Gaussian velocity fields.

Growth depends significantly on the magnetic Prandtl number.

Abstract

We consider a natural generalization of the Kazantsev-Kraichnan model for small-scale turbulent dynamo. This generalization takes account of statistical time asymmetry of a turbulent flow, and, thus, allows to describe velocity fields with energy cascade. For three-dimensional velocity field, generalized Kazantsev equation is derived, and evolution of the second order magnetic field correlator is investigated for large but finite magnetic Prandtl numbers. It is shown that as $Pr_m \to \infty$, the growth increment tends to the limit known from the T-exponential (Lagrangian deformation) method. Magnetic field generation is shown to be weaker than that in the Gaussian velocity field for any direction of the energy cascade, and depends essentially on the Prandtl number.