A New Archeomagnetic Field Intensity Variation Curve from Southern Quebec for the Past Four Centuries.

English Abstract:

New archeointensity data were obtained in Quebec from twelve groups of ceramic and brick fragments dated from the early 17th to late 19th century AD. These data were derived using the Triaxe magnetometer and a tailored experimental protocol. The results show a decrease in intensity in Quebec between the 17th and the early 18th century, followed by an increase until 1900. Similar variations are predicted in Quebec City by the gufm1 geomagnetic field models regardless of whether the calibration uses the assumption of a strong, low or null linear decrease of the dipole moment between 1600 and the mid-19th century AD. However, the amplitudes of the predicted variations appear lower than those displayed from the new data, the latter showing a marked minimum during the 18th century. These new results, together with previous data obtained in France and Brazil, argue in favor of an oscillatory behavior rather than a linear evolution of the dipole moment between 1600 and 1850.