Robust Characteristics of the Laschamp and Mono Lake Geomagnetic Excursions: Results From Global Field Models
| Autor: | Ingo Wardinski, Maxwell C. Brown, Sanja Panovska, Monika Korte |
|---|---|
| Přispěvatelé: | Jarðvísindastofnun (HÍ), Institute of Earth Sciences (UI), Verkfræði- og náttúruvísindasvið (HÍ), School of Engineering and Natural Sciences (UI), Háskóli Íslands, University of Iceland, GeoForschungsZentrum - Helmholtz-Zentrum Potsdam (GFZ), Laboratoire de Planétologie et Géodynamique [UMR 6112] (LPG), Université d'Angers (UA)-Université de Nantes - UFR des Sciences et des Techniques (UN UFR ST), Université de Nantes (UN)-Université de Nantes (UN)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS) |
| Rok vydání: | 2019 |
| Předmět: |
Paleomagnetism
010504 meteorology & atmospheric sciences Field (physics) [SDU.STU.GP]Sciences of the Universe [physics]/Earth Sciences/Geophysics [physics.geo-ph] Phase (waves) Mono lake excursion 010502 geochemistry & geophysics 01 natural sciences geomagnetic field lcsh:Science ComputingMilieux_MISCELLANEOUS 0105 earth and related environmental sciences Excursion Spherical harmonics paleomagnetism Geophysics 15. Life on land Mono Lake excursion Laschamp excursion Global magnetic field models global magnetic field models Dipole Earth's magnetic field Líkön Bergsegulmælingar General Earth and Planetary Sciences lcsh:Q Magnetic dipole Jarðsegulsvið Geology Geomagnetic field |
| Zdroj: | Frontiers in Earth Science Frontiers in Earth Science, Vol 7 (2019) Frontiers in Earth Science, Frontiers Media, 2019, 7, ⟨10.3389/feart.2019.00086⟩ |
| ISSN: | 2296-6463 |
| Popis: | Publisher's version (útgefin grein) Data-based global paleomagnetic field models provide a more complete view of geomagnetic excursions than individual records. They allow the temporal and spatial field evolution to be mapped globally, and facilitate investigation of dipole and non-dipole field components. We have developed a suite of spherical harmonic (SH) field models that span 50–30 ka and include the Laschamp (~41 ka) and Mono Lake (~33 ka) excursions. Paleomagnetic field models depend heavily on the data used in their construction. Variations in paleomagnetic sediment records from the same region are in some cases inconsistent. To test the influence of data selection and reliance on age models, we have built a series of SH models based upon different data sets. A number of excursion characteristics are robust in all models, despite some differences in energy distribution among SH coefficients. Quantities, such as field morphology at the core-mantle boundary (CMB) or individual SH degree power variations should be interpreted with caution. All models suggest that the excursion process during the Laschamp is mainly governed by axial dipole decay and recovery, without a significant influence from the equatorial dipole or non-dipole fields. The axial dipole component reduces to almost zero, but does not reverse. This results in excursional field behavior seen globally, but non-uniformly at Earth's surface. The Mono Lake excursion may be a series of excursions occurring between 36 and 30 ka rather than a single excursion. In contrast to the Laschamp, these excursions appear driven by smaller decreases in axial dipole field strength during a time when the axial dipole power at the CMB is similar to the power in the non-dipole field. We suggest three phases for the 50 to 30 ka period: (1) a broadly stable phase dominated by the axial dipole (50–43 ka); (2) the Laschamp excursion, with the underlying excursion process lasting ~5 ka (43–38 ka) and the surface field expression lasting ~2 ka (42–40 ka); (3) a weak phase during which axial dipole and non-dipole power at the CMB are comparable, leading to more than one excursion between 36 and 30 ka. MB was supported by the Deutsche Forschungsgemeinschaft SPP PlanetMag 1488 project BR4697/1. |
| Databáze: | OpenAIRE |
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