ABSTRACT
This chapter is devoted to the planet for which we have the best knowledge, namely the Earth. We will review observational facts about the Earth’s magnetic field in Section 4.1. We review the equations and parameters relevant to the Geodynamo in Section 4.2. We elaborate on the theoretical results outlined in Chapter 1 to derive the fundamental results appropriate to the Earth’s core in Section 4.3. The existing constraints on the control parameters are addressed in Section 4.4. We then discuss the present status of numerical geodynamo models in Section 4.5. We focus then on the difficult problem of the small scale turbulent flow in the Earth’s core in Sections 4.6 to 4.10.2. Next, we touch on some relevant geophysical issues (Section 4.7). Then (Section 4.8), we shall expound the traditional method, the insights it gives and the difficulties it faces. This is followed (Section 4.9) by a description of the engineering approach. Finally we discuss future developments on the geodynamo and a critique of turbulence in Section 4.10.
