The cooling-rate effect on microwave archeointensity estimates

Autor(es)

Poletti, Wilbor ^{[1, 2]} ; Hartmann, Gelvam A. ^[2] ; Hill, Mimi J. ^[1] ; Biggin, Andrew J. ^[1] ; Trindade, Ricardo I. F. ^[2]

Afiliação do(s) autor(es)

^[1] Univ Liverpool, Dept Earth Ocean & Ecol Sci, Geomagnetism Lab, Liverpool L69 3BX, Merseyside - England

^[2] Univ Sao Paulo, Dept Geofis, Inst Astron Geofis & Ciencias Atmosfer, BR-05508090 Sao Paulo - Brazil

• Tipo de documento: Artigo Científico
• Fonte: Geophysical Research Letters; v. 40, n. 15, p. 3847-3852, AUG 16 2013.
• Citações Web of Science: 8

Resumo

New microwave (MW) paleointensity data on historical bricks from Northeast Brazil presented a bias toward higher fields when compared to previous cooling-rate corrected double-heating paleointensity estimates; the same relates to the previously reported values for pottery from Southwestern Pacific islands. A simple theoretical approach suggests that the MW bias in both collections is due to a cooling-rate effect on MW estimates. We then experimentally corrected the MW cooling-rate effect on Brazilian fragments, increasing the degree of consistency between the previous and new results (reducing discrepancies from 25% to 8%). Results indicate similar experimental behavior between microwave and thermal procedures despite the different ways in which the energy is transferred into the spin system. Finally, they allow cooling times of less than 90s to be empirically estimated in most of these MW experiments highlighting the need for systematic cooling-rate corrections to be applied in similar MW paleointensity studies in the future. (AU)

• Processo FAPESP: 10/10754-4 - Evolução do campo magnético terrestre na América do Sul para os últimos 500 anos
• Beneficiário: Gelvam André Hartmann
• Modalidade de apoio: Bolsas no Brasil - Pós-Doutorado