Mantle Electrical Conductivity and the Magnetic Field at the Core–Mantle Boundary

The Earth’s magnetic field is measured on and above the crust, while the turbulent dynamo in the outer core produces magnetic field values at the core–mantle boundary (CMB). The connection between the two sets of values is usually assumed to be independent of the electrical conductivity in the mantl...

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Autor principal:	John V. Shebalin
Formato:	article
Lenguaje:	EN
Publicado:	MDPI AG 2021
Materias:	geomagnetism core–mantle boundary electrical conductivity Thermodynamics QC310.15-319 Descriptive and experimental mechanics QC120-168.85
Acceso en línea:	https://doaj.org/article/c79ebd4f6c5849478bf77b675d8b9eeb
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spelling	oai:doaj.org-article:c79ebd4f6c5849478bf77b675d8b9eeb2021-11-25T17:31:41ZMantle Electrical Conductivity and the Magnetic Field at the Core–Mantle Boundary10.3390/fluids61104032311-5521https://doaj.org/article/c79ebd4f6c5849478bf77b675d8b9eeb2021-11-01T00:00:00Zhttps://www.mdpi.com/2311-5521/6/11/403https://doaj.org/toc/2311-5521The Earth’s magnetic field is measured on and above the crust, while the turbulent dynamo in the outer core produces magnetic field values at the core–mantle boundary (CMB). The connection between the two sets of values is usually assumed to be independent of the electrical conductivity in the mantle. However, the turbulent magnetofluid in the Earth’s outer core produces a time-varying magnetic field that must induce currents in the lower mantle as it emerges, since the mantle is observed to be electrically conductive. Here, we develop a model to assess the possible effects of mantle electrical conductivity on the magnetic field values at the CMB. This model uses a new method for mapping the geomagnetic field from the Earth’s surface to the CMB. Since numerical and theoretical results suggest that the turbulent magnetic field in the outer core as it approaches the CMB is mostly parallel to this boundary, we assume that this property exists and set the normal component of the model magnetic field to zero at the CMB. This leads to a modification of the Mauersberger–Lowes spectrum at the CMB so that it is no longer flat, i.e., the modified spectrum depends on mantle conductance. We examined several cases in which mantle conductance ranges from low to high in order to gauge how CMB magnetic field strength and mantle ohmic heat generation may vary.John V. ShebalinMDPI AGarticlegeomagnetismcore–mantle boundaryelectrical conductivityThermodynamicsQC310.15-319Descriptive and experimental mechanicsQC120-168.85ENFluids, Vol 6, Iss 403, p 403 (2021)
institution	DOAJ
collection	DOAJ
language	EN
topic	geomagnetism core–mantle boundary electrical conductivity Thermodynamics QC310.15-319 Descriptive and experimental mechanics QC120-168.85
spellingShingle	geomagnetism core–mantle boundary electrical conductivity Thermodynamics QC310.15-319 Descriptive and experimental mechanics QC120-168.85 John V. Shebalin Mantle Electrical Conductivity and the Magnetic Field at the Core–Mantle Boundary
description	The Earth’s magnetic field is measured on and above the crust, while the turbulent dynamo in the outer core produces magnetic field values at the core–mantle boundary (CMB). The connection between the two sets of values is usually assumed to be independent of the electrical conductivity in the mantle. However, the turbulent magnetofluid in the Earth’s outer core produces a time-varying magnetic field that must induce currents in the lower mantle as it emerges, since the mantle is observed to be electrically conductive. Here, we develop a model to assess the possible effects of mantle electrical conductivity on the magnetic field values at the CMB. This model uses a new method for mapping the geomagnetic field from the Earth’s surface to the CMB. Since numerical and theoretical results suggest that the turbulent magnetic field in the outer core as it approaches the CMB is mostly parallel to this boundary, we assume that this property exists and set the normal component of the model magnetic field to zero at the CMB. This leads to a modification of the Mauersberger–Lowes spectrum at the CMB so that it is no longer flat, i.e., the modified spectrum depends on mantle conductance. We examined several cases in which mantle conductance ranges from low to high in order to gauge how CMB magnetic field strength and mantle ohmic heat generation may vary.
format	article
author	John V. Shebalin
author_facet	John V. Shebalin
author_sort	John V. Shebalin
title	Mantle Electrical Conductivity and the Magnetic Field at the Core–Mantle Boundary
title_short	Mantle Electrical Conductivity and the Magnetic Field at the Core–Mantle Boundary
title_full	Mantle Electrical Conductivity and the Magnetic Field at the Core–Mantle Boundary
title_fullStr	Mantle Electrical Conductivity and the Magnetic Field at the Core–Mantle Boundary
title_full_unstemmed	Mantle Electrical Conductivity and the Magnetic Field at the Core–Mantle Boundary
title_sort	mantle electrical conductivity and the magnetic field at the core–mantle boundary
publisher	MDPI AG
publishDate	2021
url	https://doaj.org/article/c79ebd4f6c5849478bf77b675d8b9eeb
work_keys_str_mv	AT johnvshebalin mantleelectricalconductivityandthemagneticfieldatthecoremantleboundary
_version_	1718412252884762624

Mantle Electrical Conductivity and the Magnetic Field at the Core–Mantle Boundary

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