Earth Planets Space, Vol. 59 (No. 7), pp. 651-659, 2007
Paul H. Roberts1 and Masaru Kono2
1Institute of Geophysics and Planetary Physics, University of California, Los Angeles, CA90095, U.S.A.
2Global Edge Institute, Tokyo Institute of Technology, Meguro-ku, Tokyo 152-8551, Japan
(Received January 7, 2007; Revised May 9, 2007; Accepted May 11, 2007; Online published July 20, 2007)
The energy budget of the Earth's core balances the heat lost through cooling with the sum of gravitational, latent heat and radioactive sources (if any). The gravitational and latent heat sources are due to the freezing of core mix onto the surface of the inner core. Gravitational energy is released because the light components of core mix that are released during freezing are buoyant, and rise as they rejoin the fluid core. This source of energy can be regarded as part of the total gravitational energy released as the entire Earth cools and contracts. The main purpose of this paper is to present a new method of evaluating the total energy release. The method is applied to two Earth models. Both show that the gravitational source that stirs the fluid core is less than 30% of the total gravitational energy released through the contraction of the Earth as it cools.
Key words: Earth's core, thermal evolution, inner core growth, core convection, geodynamo.