Hydromagnetic quasi-geostrophic modes in rapidly rotating planetary cores

TL;DR

This paper studies the properties of hydromagnetic quasi-geostrophic modes in rapidly rotating planetary cores, focusing on how magnetic field strength, rotation rate, and magnetic dissipation influence these eigenmodes.

Contribution

It provides a detailed analysis of the behavior of hydromagnetic quasi-geostrophic modes under various planetary core conditions, highlighting their dependence on key non-dimensional parameters.

Findings

Identification of how magnetic field strength affects mode characteristics

Demonstration of the influence of rotation rate on mode frequencies

Analysis of magnetic dissipation's impact on mode stability

Abstract

The core of a terrestrial-type planet consists of a spherical shell of rapidly rotating, electrically conducting, fluid. Such a body supports two distinct classes of quasi-geostrophic eigenmodes: fast, primarily hydrodynamic, inertial modes with period related to the rotation time scale and slow, primarily magnetic, magnetostrophic modes with much longer periods. Here, we investigate the properties of these hydromagnetic quasi-geostrophic modes as a function of non-dimensional parameters controlling the strength of the background magnetic field, the planetary rotation rate, and the amount of magnetic dissipation. ... read full length abstract in the paper.