抄録
The effect of electromagnetic core-mantle coupling on small changes in the length of day and the geographical location of the pole is treated by a simplified model which neglects the time required for magnetic diffusion through the lower mantle, and approximates the poloidal field by the centred dipole. The resulting formulae for the time constants of the coupling are more meaningful physically than, and give nearly the same numerical values as, those derived previously by more rigorous methods. It is shown that, despite the complexity of the electromagnetic interactions at the coremantle boundary, the two kinds of perturbation in the Earth's rotation can be treated independently. Simple expressions are given for the electromagnetic restoring torque on the accelerating mantle. The effect of the geomagnetic coupling on the diurnal wobble is discussed, and concluded to be negligible.
