Baroclinic Instability in Differentially Rotating Stars

TL;DR

This paper analyzes the onset and characteristics of baroclinic instability in differentially rotating stellar radiation zones, revealing rapid growth, wave families involved, and potential magnetic field generation.

Contribution

It provides a linear analysis of baroclinic instability in stellar radiation zones with differential rotation, identifying instability conditions and implications for magnetic field generation.

Findings

Instability occurs at very small rotation inhomogeneity.

Two families of unstable disturbances are identified: Rossby and gravity waves.

Growth time of the instability is short compared to stellar evolution.

Abstract

A linear analysis of baroclinic instability in a stellar radiation zone with radial differential rotation is performed. The instability onsets at a very small rotation inhomogeneity. There are two families of unstable disturbances corresponding to Rossby waves and internal gravity waves. The instability is dynamical: its growth time of several thousand rotation periods is short compared to the stellar evolution time. A decrease in thermal conductivity amplifies the instability. Unstable disturbances possess kinetic helicity thus indicating the possibility of magnetic field generation by the turbulence resulting from the instability.