A New Mechanism for the Joule Heating of Moons and Planets - Livestream

Two forms of joule heating of celestial bodies (and, in particular, planetary satellites) have received particular attention: unipolar-generator heating with currents running between the primary and secondary, and magnetic induction heating due to the primary’s time-varying field. Neither appears to cause significant dissipation in the contemporary solar system. But these discussions have overlooked heating derived from the spatial variation of the primary’s field across the interior of the secondary. This leads to Lorentz-force-driven currents around paths entirely internal to the secondary, with resulting ohmic heating. I will describe three ways to drive such currents, and show that the first of these operates even for a spin-locked secondary whose orbit has zero eccentricity, in strong contrast to tidal dissipation. Jupiter’s moon Io today could dissipate about 600 GW (more than its likely radiogenic heating) by this mechanism. Had Io ever been at 3 Jovian radii instead of its current 5.9, it could have been dissipating 15,000 GW. This mechanism could drive inward orbital migration of secondaries, in thissolar system or others. I will close my talk with a brief description of theoretical and experimental work regarding some surprising implications of Earth’s apparent rotation through the axially symmetric components (with respect to its rotation axis) of its own magnetic field.

Speaker: Christopher Chyba, Princeton University

See weblink for Zoom information