Energy Flow and Producing the Earth’s Magnetic Field—The Dynamo

A historical review of mechanical dynamos is given. It shows how mankind learned how to make an electric field and a magnetic field sustain each other to produce electricity. Like convection, a value of forcing must be exceeded before the production of an electromagnetic field can exist; hence the electromagnetic field is an energy-flow structure. Flow in Earth’s metallic liquid core was known to be one of the most likely candidates to produce Earth’s magnetic field, but calculation of the fluid flow needed for this production was not successful until the 1970s. Solving how this flow works (called the dynamo problem) required the development of electromagnetic fluid dynamics studies. Finally, full dynamo calculations were completed on numerical computers so that today many of the features of Earth’s dynamo are being investigated.