Electromagnetic and Viscous Damping of Core Oscillations

A detailed investigation of the interaction of core oscillations with the main magnetic field is made. Selection rules and interaction coefficients are obtained. Although the strengths of the interactions vary over nearly three orders of magnitude, all are extremely weak. Ohmic and viscous dissipation are considered in parallel calculations. It is found that core oscillations are almost unaffected by either damping mechanism. Most of the Ohmic dissipation takes place within a few skin depths of the boundary. Viscous dissipation is estimated only for the body of the liquid core. Even though it is expected to be much larger near the boundaries, it would seem unlikely to be sufficiently large to be of any significance. Our conclusion is that core oscillations are virtually free of damping. In a subadiabatic core, gravitational oscillations might be persistent enough to sustain an oscillatory geodynamo.