Stability of Baroclinic Flows in a Zonal Magnetic Field: Part II

Abstract

The equations of Part I are approximated to represent a two-layer model. All the theorems for the continuous case are shown to hold in the two-layer case as well. In addition, bounds are placed on the phase velocities of neutral waves. The stability of purely baroclinic flow (no horizontal shear) in a uniform zonal magnetic field is then studied. The minimum vertical shear needed for instability no longer depends upon the ?-effect or the static stability, but rather is determined by the zonal field strength. Short waves are destabilized by the magnetic field, long waves stabilized. Unstable waves convert available potential energy into kinetic energy of the disturbances, part of which in turn is converted into disturbance magnetic energy. Nonmagnetic changes in the initial state are similar to those of Phillips. Perturbation vertical magnetic fields and a single-celled meridional (poloidal) field are produced.