The dynamo problem and the geomagnetic field

It is probable that the major part of the Earth's magnetic field is generated by processes of electromagnetic induction within the liquid core of the Earth. Following a discussion of the general problem of producing magnetic fields in a body of electrically conducting fluid such as the Earth's core, some of the many different attempts at solving this difficult problem are described. The properties of the core, and possible sources of the energy of the geomagnetic field are then considered, and the manner in which this dynamo process for generating magnetic fields might operate within the Earth is reviewed.