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Spatio-temporal variations of archeomagnetic flux patches

Grant number: 13/14629-8
Support Opportunities:Scholarships abroad - Research Internship - Scientific Initiation
Effective date (Start): August 15, 2013
Effective date (End): December 14, 2013
Field of knowledge:Physical Sciences and Mathematics - Geosciences - Geophysics
Principal Investigator:Gelvam André Hartmann
Grantee:Filipe Terra Nova dos Santos
Supervisor: Hagay Amit
Host Institution: Instituto de Astronomia, Geofísica e Ciências Atmosféricas (IAG). Universidade de São Paulo (USP). São Paulo , SP, Brazil
Research place: Université de Nantes, France  
Associated to the scholarship:12/24658-2 - Physical parameters of the non-dipole components of the geomagnetic field, BP.IC


The geomagnetic field originated at Earth's outer core is characterized for the dipolar and non-dipolar parts. Non-dipolar field variations over the past few centuries and millennia seem to be responsible for the decreasing of the dipole field moment as well as for the evolution of the large-scale non-dipolar features, particularly the South Atlantic Magnetic Anomaly (SAMA). The SAMA represents the lowest field intensities values on Earth's surface. It is intrinsically related to the flow patterns of the conducting fluid at the outer core, especially due to the reversal flux patches observed at core-mantle boundary (CMB). Non-dipole field variations at Earth's surface could be associated with non-zonal oscillations, which need a detailed analysis at CMB. Until now, we have developed an algorithm (called fpf01) to determine the flux patches at CMB. The fpf01 algorithm searches automatically the maxima and minima of the vertical field values at CMB by applying a discretization in a matrix of all intensity data. Preliminary results show that values do not present any gaps in time for some persistent flux patches, which allow us to track them continuously in space. The algorithm fpf01 could only track the maximum/minimum point for each flux patch. However, it is clear that not only a data point represents a flux patch, but normal (or reverse) geomagnetic field lines affect a region at CMB. This work has two main objectives: (a) Improve algorithm fpf01 to track flux patches at CMB, (b) Develop a spectral analysis of the flux patches tracked through the past few millennia. It could provide information about temporal behavior (periodic, chaotic and/or stochastic) and the possible physical mechanisms of the flux patches, by the light of the Earth's core dynamics theory. (AU)

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Scientific publications
(References retrieved automatically from Web of Science and SciELO through information on FAPESP grants and their corresponding numbers as mentioned in the publications by the authors)
TERRA-NOVA, FILIPE; AMIT, HAGAY; HARTMANN, GELVAM A.; TRINDADE, RICARDO I. F.. The time dependence of reversed archeomagnetic flux patches. JOURNAL OF GEOPHYSICAL RESEARCH-SOLID EARTH, v. 120, n. 2, p. 691-704, . (10/10754-4, 13/14629-8)

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