The time dependence of reversed archeomagnetic flux patches. Issue 2 (18th February 2015)

• Record Type: Journal Article
• Authors: Terra‐Nova, Filipe; Amit, Hagay; Hartmann, Gelvam A.; Trindade, Ricardo I. F.
• Is Part Of: Journal of geophysical research. Volume 120:Issue 2(2015:Feb.)
• Page Start: 691
• Page End: 704
• Publication Date: 2015-02-18
• Subjects: reversed flux patches -- archeomagnetic field -- core‐mantle boundary -- axial dipole moment -- magnetic equator; Geomagnetism -- Periodicals; Geochemistry -- Periodicals; Geophysics -- Periodicals; Earth sciences -- Periodicals; 551.1
• DOI: 10.1002/2014JB011742
• Languages: English
• ISSNs: 2169-9313

Abstract

Abstract: Archeomagnetic field models may provide important insights to the geodynamo. Here we investigate the existence and mobility of reversed flux patches (RFPs) in an archeomagnetic field model. We introduce topological algorithms to define, identify, and track RFPs. In addition, we explore the relations between RFPs and dipole changes and apply robustness tests to the RFPs. In contrast to previous definitions, patches that reside on the geographic equator are adequately identified based on our RFPs definition. Most RFPs exhibit a westward drift and migrate toward higher latitudes. Undulations of the magnetic equator and RFPs oppose the axial dipole moment (ADM). Filtered models show a tracking behavior similar to the nonfiltered model, and surprisingly new RFPs occasionally emerge. The advection and diffusion of RFPs have worked in unison to yield the decrease of the ADM at recent times. The absence of RFPs in the period 550–1440 A.D. is related to a low in intermediate degrees of the geomagnetic power spectrum. We thus hypothesize that the RFPs are strongly dependent on intermediate spherical harmonic degrees 4 and above. Key Points: Most RFPs exhibit westward drift and almost all migrate to higher latitudes Advection and diffusion of RFPs explain the historical decrease in the ADM Spherical harmonic degrees 4 and above strongly affect the existence of the RFPs