ERSC 3P12 Lecture Notes - Lecture 11: Pelagic Sediment, Cosmogenic Nuclide, Cosmic Ray
22 May 2016
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36,000 years, spontaneous reversal, took just over 1000 years. (1) 500 years before middle of reversal; (2) middle of reversal; (3) 500 years after middle of reversal. Intensity of dipole moment decreased by a factor of 10 during reversal, but recovered immediately after, exactly as seen in the rock record. Many failed attempts, probably caused by the more stable magnetic field of the inner core solid so can only change by diffusion. Model then allowed to run with: uniform heat flux out of the core no reversal. heterogenous heat flux out of the core two more reversals, approx. Heat output from core has important effect on frequency of reversals. Independent studies show that earth"s inner core is super-rotating at 1 /yr (interaction with magnetic field of outer core) and its eastern hemisphere is seismically isotropic, western hemisphere anisotropic. Adds complexity to understanding the control of the inner core on reversals and polar wander.
