There is much renewed interest in the energetics of the core because of its relevance to the thermal history of the Earth and the ability for magnetic field generation to take place over geological time. Here we present the results of calculations to place lower bounds on both the Ohmic dissipation and the entropy production rate. To do so we adopt the constraints arising from geodetic studies of the Earth's nutations. Buffett and coworkers deduce the field strength at the core-mantle and inner-core boundaries necessary to produce the required dissipation mechanism to account for the out-of-phase response of the Earth to the planetary driving mechanisms. We use these in tandem with geomagnetic constraints in a variational procedure to determine precise lower bounds on the quantities of interest. Whilst these lower bounds are, by their very nature, underestimates of the true dissipations, the results are actually approaching (within an order of magnitude) several recent estimates of the Ohmic dissipation. We will discuss the results, areas of uncertainty and possible future avenues of investigation.
 

Convenor:Louis Moresi, Richard Wardle