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EP: Fachverband Extraterrestrische Physik
EP 6: Planets and small Objects
EP 6.4: Talk
Thursday, September 2, 2021, 12:00–12:15, H8
New dynamo models with a stably stratified layer as an explanation for Mercury's unique magnetic field — •Patrick Kolhey1, Daniel Heyner1, Johannes Wicht2, and Karl-Heinz Glassmeier1 — 1Institut für Geophysik und extraterrestrische Physik, TU Braunschweig — 2Max Planck Institute for Solar System Research, Göttingen
Since the discovery of Mercury's peculiar magnetic field it has raised questions about the dynamo process in the fluid core. The surface magnetic field is rather weak, strongly aligned to the planet's rotation axis and its magnetic equator is shifted towards north. Especially the latter characteristic is difficult to explain using common dynamo model setups. One promising model suggests a stably stratified layer right underneath the core-mantle boundary. As a consequence the magnetic field deep inside the core is efficiently damped by passing through the stably stratified layer due to a so-called skin effect. Additionally, the non-axisymmetric parts of the magnetic field are vanishing, too, such that a dipole dominated magnetic is left at the planet's surface. In this study we present new direct numerical simulations of the magnetohydrodynamical dynamo problem which include a stably stratified layer on top of the outer core, which can also reproduce the shift of the magnetic equator towards north. We explore a wide parameter range, varying mainly the Rayleigh and Ekman number under the aspect of a strongly stratified layer. We show which conditions are necessary to produce a Mercury-like magnetic field and give a inside about the planets interior structure.