| Texto completo | |
| Autor(es): |
Ramires, Luiza G.
;
Hartmann, Gelvam A.
;
Poletti, Wilbor
;
Caprara, Barbara B.
;
Coppi, Daniel
;
Alves, Renata N.
;
Mandarino, Marcelle
;
Gaspar, Maria D.
;
de Souza, Marcos Andre Torres
;
Trindade, Ricardo I. F.
Número total de Autores: 10
|
| Tipo de documento: | Artigo Científico |
| Fonte: | Earth and Planetary Science Letters; v. 671, p. 12-pg., 2025-10-15. |
| Resumo | |
The primary sources for studying the Earth's magnetic field variations come from field observations taken at the Earth's surface, which are essential for modeling purposes. However, the limited availability of high-quality data in the southern hemisphere significantly hinders our understanding of field evolution, particularly regarding major features such as the South Atlantic Anomaly over centennial to millennial timescales. In this study, we present six new high-quality archeointensity averages obtained from brick fragments in Southeastern Brazil. By employing a classical double-heating protocol along with partial thermoremanent magnetization checks (pTRMchecks), pTRM-tail checks, and corrections for anisotropy and cooling rates, we achieved a success rate of 54%. Our results indicate a decline in geomagnetic field intensity from approximately 39 mu T around 1740 +/- 50 CE to about 27 mu T in 1918 +/- 2 CE. Furthermore, a wavelet analysis using both speleothem and archeointensity records reveals a distinct periodicity of approximately 64-128 years attributed to non-dipole contributions to the geomagnetic field during the period from 1200 to 1700 CE. This periodicity closely resembles that observed in geomagnetic field models and data from the historical field. The analysis suggests that around the lowest recorded values of non-dipole contributions, approximately 1600 CE, the characteristics of the dipole begin to show a significant decrease. This observation raises important questions about the relationship between these two phenomena. A more comprehensive investigation is warranted to clarify these dynamics and their implications for understanding the behavior of the geomagnetic field over time. (AU) | |
| Processo FAPESP: | 22/03086-2 - História geomagnética da América do Sul |
| Beneficiário: | Gelvam André Hartmann |
| Modalidade de apoio: | Auxílio à Pesquisa - Projeto Inicial |
| Processo FAPESP: | 23/04179-7 - EMU concedido no processo 2022/03086-2: magnetômetro spinner automático JR-6A (AGICO) |
| Beneficiário: | Gelvam André Hartmann |
| Modalidade de apoio: | Auxílio à Pesquisa - Programa Equipamentos Multiusuários |