Magnetohydrodynamics of the earth's dynamo

It is currently generally accepted that the earth's magnetic field is generated by motions in the liquid part of the earth's core. The details of this process, however, are still unresolved. An attempt is made to outline the theoretical problems associated with this process and to describe some of the advances made in recent years. The mathematical problem concerned with the generation of magnetic fields by motion in an electrically conducting fluid is called the dynamo problem. The dynamo process converts mechanical energy into magnetic energy and dissipates it in the form of ohmic heat. Questions concerning the energy source of the earth's magnetic field are considered in connection with a discussion of the physical state of the earth's core. It is shown that the dynamics of motions in the earth's core are dominated by the Coriolis force rather than the energy-providing forces. At the present time the basic dynamo mechanism has been understood well enough and the problem of a development of quantitative models for the geodynamo can be attacked.