Abstract
The essence of the dynamo theory of the earth's main magnetic field is that we have groups of magnetic fields which can be maintained stationarily by some fluid motions of a certain magnitude. The problem considered here is what the time characteristics of these groups of magnetic fields are when driven by motions of larger or smaller magnitude than those required just to keep the fields stationary. As expected, when driven by motions of larger or smaller magnitude, the fields develop or decay exponentially. In the second half of this paper, we have simplified the mathematics of induction of T20 field from S10 field by T10 motion, which is the most important process in the dynamo theory of the earth's magnetic field.
