A new simple idealised model for the geodynamo is proposed. In this model,
the energy required for the self-exciting dynamo action is provided by
thermal convection in a Welander loop; this is coupled with two Bullard
disc dynamos. It is found that two discs with opposite `twists' are
required in order to achieve reversals of the magnetic field, and the
model can then be described by a dynamical system of 5th order.
This system is found to be identical to the 5th order
system of Kennett (1976) resulting from a truncation of the full
magnetohydrodynamic equations. The bifurcation structure of the system is
studied, and numerical solutions are presented.
This paper is published in
Chui, A.Y.K. & Moffatt, H.K. 1993 (d11.ps.gz, 77K, 8 pages)
A thermally driven disc dynamo.
In Solar and Planetary Dynamos
(ed. Proctor, M.R.E. et al.), pp. 51-58. CUP.
A Thermally Driven Disc Dynamo