The Periodical Self-exciting Fluid Dynamos

Abstract

Assuming the fluid motion of v_T1°-type (expression (3.1) in §3), we have studied here the time characteristics of self-exciting fluid dynamos. As a result of theoretical calculations, it has been found that three magnetic fields expressed by three surface spherical harmonics Y^m_n-1, Y^m_n and Y^m_n+1((n, m)-harmonics in §3) can coexist independently of other magnetic fields. These three magnetic fields oscillate concurrently in intensity quasi-periodically with time, the frequency being proportional to order m, fluid velocity and depth of the fluid layer. The westward drift of the earth's magnetic field and also the reversal of the magnetic field of the sun may be well explained by the above results. The periodical dynamo presented here may also be appropriate as a model for magnetic variable stars.