How do planets maintain their magnetic fields?

How do planets maintain their magnetic fields?

This is a past event


Despite over 70 years of concerted research, we still do not understand the detailed mechanism by which the planets maintain their magnetic fields. While all agree that such fields are examples of fluid dynamos, driven by strongly turbulent convection within the planet's interior, there is still no agreement as to how such a strongly stochastic flow can maintain a simple, quasi-steady dipolar magnetic field aligned with the rotation axis. Nor is there any agreement as to why that dipole occasionally reverses. Some numerical simulations of planetary dynamos manage to reproduce plausible looking magnetic fields, but they operate in a regime which is very far from that of a planet, and so it is hard to gauge which, if any, of the key dynamical processes at work in the numerical dynamos could operate in a planetary interior.       In this seminar we review the evidence of the numerical simulations and actual planetary dynamos, identify their similarities and differences, and propose a simple cartoon for the maintenance of a dipolar field, a cartoon that is consistent with what we observe.

Short Biography of Professor Peter Davidson:

Born in Aberdeen in 1957, Peter Davidson graduated in engineering from Aberdeen University in 1979. Following several years in industry, both in the UK and the USA, and a PhD in Cambridge, he joined the Mechanical Engineering Department at Imperial College as a lecturer in 1989. He transferred back to Cambridge Engineering Department in 1994, where he has been ever since. His research interests include industrial and astrophysical applications of magnetohydrodynamics as well as turbulent flow. His current research centres on tropical cyclones, planetary dynamos and liquid-metal batteries for grid storage. He won the Institute of Materials prize for the best paper on non-ferrous metals in 1994, was the principal organizer of the 2008 Isaac Newton Institute 4 months turbulence programme, was a visiting professor at Ecole Normale Supérieure in 2015, is a co-organiser the upcoming 2020 Isaac Newton Institute programme in stellar and planetary dynamos, and has been an associate editor of J. Fluid Mechanics since 2000. He is the author of several books, including textbooks on turbulence, electrodynamics and magnetohydrodynamics.

Professor Peter Davidson
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