Recent progress in identification of the geomagnetic signature of 3D outer core flows
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Recent progress in identification of the geomagnetic signature of 3D outer core flows Lukács Kuslits1 · István Lemperger1 · András Horváth2 · Dávid Koronczay1,3 · Viktor Wesztergom1 Received: 14 May 2020 / Accepted: 26 July 2020 / Published online: 14 August 2020 © The Author(s) 2020
Abstract A summary of methods yielding information about the generation and configuration of the geomagnetic main field is presented with special focus on complications concerning these methods. A global source model constructed with the help of machine learning (and deep learning) is proposed to mitigate these issues, in particular the uncertainties caused by vigorous convection and small scale fields. Keywords Geomagnetism · Core dynamo · Machine learning
1 Introduction Acquiring valid information on planetary interiors is an elusive scientific objective hampered by the obvious impossibility of in situ measurements and a handful of non-trivial complications. In case of the Earth the presence of a relatively large magnetic field and its changes are helpful in studying the internal processes of the planet, since the main geomagnetic field observed at the surface originates from dynamo processes of the fluid outer core. Mathematical representation of the field and its slow gradual change to unprecedented accuracy are obtained from ground based observations and satellite missions. This paper intends to provide a short summary of our present knowledge on the generating processes of the main geomagnetic field along with the scientific inquiries which have revealed these pieces of information. The main difficulties or constraints concerning each area of investigation are briefly described as well. On the basis of these, the paper demonstrates the raison d’être of a machine learning based approach of the problem of core field reconstruction. * Lukács Kuslits [email protected] 1
Geodetic and Geophysical Institute, Research Centre for Astronomy and Earth Sciences, Eötvös Loránd Research Network, Sopron, Hungary
2
Faculty of Information Technology and Bionics, Pázmány Péter Catholic University, Budapest, Hungary
3
Space Research Group, Eotvos University, Budapest, Hungary
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Vol.:(0123456789)
348
Acta Geodaetica et Geophysica (2020) 55:347–370
The main conclusion of the study points to the necessity of a global source model of the core field, which is at present missing as a tool of gaining and validating information on the geodynamo, especially at processes of shorter spatial scales.
2 Recent knowledge on consistency and composition of the core: geomagnetic dynamo aspects First indications to a liquid central region within the Earth’s interior come from the determination of a shadow-zone affecting seismic shear waves by Oldham (1906), who already attributed this to a solid–liquid phase transition from the mantle to the core. Gutenberg (1912) provided a depth for the Core Mantle Boundary (CMB) at approximately 2900 km based on the seismic velocity profiles. Lehmann (1936) found that the core can be further separated
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