Direct and inverse cascades in the geodynamo

TL;DR

This paper investigates the energy transfer processes in planetary geodynamo models, demonstrating the coexistence of forward and inverse cascades and analyzing magnetic field saturation mechanisms.

Contribution

It introduces a model capturing small-scale geostrophic flows and provides estimates of energy fluxes, highlighting the dual cascades in planetary magnetic field generation.

Findings

Demonstration of simultaneous forward and inverse cascades.

Estimates of kinetic and magnetic energy fluxes across wave numbers.

Analysis of magnetic field saturation mechanisms.

Abstract

The rapid rotation of planets causes cyclonic thermal turbulence in their cores which may generate the large-scale magnetic fields observed outside the planets. We consider the model which enables us reproduce the typical features of small-scale geostrophic flows in physical and wave spaces. We present estimates of kinetic and magnetic energy fluxes as a function of the wave number. The joint existence of forward and inverse cascades are demonstrated. We also consider the mechanism of magnetic field saturation at the end of the kinematic dynamo regime.