Baroclinic instability in differentially rotating stars

A linear analysis of baroclinic instability in a stellar radiation zone with radial differential rotation is performed. The instability sets in at a very small rotation inhomogeneity, ΔΩ ～ 10^?3Ω. There are two families of unstable disturbances corresponding to Rossby waves and internal gravity waves. The instability is dynamical: its growth time is several thousand rotation periods but is short compared to the stellar evolution time. A decrease in thermal conductivity amplifies the instability. Unstable disturbances possess kinetic helicity. Magnetic field generation by the turbulence resulting from the instability is possible.