On effect of precession-induced flows in the liquid core for early Earth's history

Abstract

Abstract. Secondary and tertiary flow patterns seen in experiments simulating flow in the Earth's liquid core induced by luni-solar precession of the solid mantle (Vanyo et al., 1995) hint at the development of non-axisymmetric columnar periodic structures. A simple interpretation of the structure formation is presented in a hydrodynamic approach. It is suggested that if similar flow patterns can occur in the Earth's liquid core enclosed into precessing and rotating mantle then kinematic of the flows may be regarded as a possible geodynamo mechanism for early Earth's history (before the solid core formation).

Evidence for a Geodynamo Driven by Thermal Energy in the Outermost Core and by Precession Deeper in the Outer Core

“…Given the VGP sequences and changes in intensities during reversals, the first major feature to be explained is the massive decrease in the intensity of the main geomagnetic axial dipole field of more than an order of magnitude and lasting at least ~15,000 years. Given also a precession driven dynamo, this major decay suggests a failure of field generation by the proposed third order flow, which gives the columns with alternating cyclonic flow and anticyclonic flow towards and from the equatorial plane in the strongly columnar regime [26,27].…”

Magnetic field dynamos and magnetically triggered flow instabilities

“…A mass of 6 tons of liquid sodium, set into motion only by the simultaneous rotation around two axes, without using any impellers or guiding blades, may indeed be considered the paradigm of a homogenous hydromagnetic dynamo. Precession has long been discussed as an energy source of the geodynamo (Malkus 1968, Kerswell 1993, Tilgner 2005, Tilgner 2007, Wu and Roberts 2009, Shalimov 2006, Nore et al 2011, Goepfert and Tilgner 2016) and the ancient lunar dynamo (Dwyer et al 2012, Noir and Cebron 2013, Weiss and Tikoo 2014, and the link between various Milankovic cycles of the Earth's orbit parameters and the occurrence of reversals (Consolini andDe Michelis 2003, Fischer et al 2009) makes it a very interesting subject of geophysics in general.…”

“…These comprise, first, a truly homogeneous dynamo in form of a large-scale precession experiment. Besides thermal and compositional buoyancy, precession has long been discussed as an alternative, or at least additional, power source of the geodynamo (Malkus 1968, Kerswell 1993, Tilgner 2005, Tilgner 2007, Wu and Roberts 2009, Shalimov 2006, the ancient lunar dynamo (Dwyer et al 2011, Noir and Cebron 2013, Weiss and Tikoo 2014, or the asteroid Vesta (Fu et al 2002). The second experiment will deal with different versions of the MRI, and their combinations with the TI, with the main goal to find the "holy grail" of this research field, which is standard MRI (SMRI) with a purely axial field being applied (Velikhov 1959, Balbus andHawley 1991).…”