Analyzing the geomagnetic axial dipole field moment over the historical period from new archeointensity results at Bukhara (Uzbekistan, Central Asia)

摘要: Abstract Since the mid-19th century, direct measurements of both intensity and directions Earth's magnetic field have been available, allowing an accurate determination its spatio-temporal variations. Prior to this time, between ∼1600 1840, only directional are available. Therefore, construction global models over period requires either a specific treatment axial dipole component or use archeomagnetic data. In study, we regional approach based on archeointensity variation curve in Central Asia. We analyze baked clay brick fragments sampled Bukhara (Uzbekistan), dated end 16th century beginning 19th century. This city is particular interest for archeomagnetism due well-preserved old buildings accurately by documentary archives. A series results obtained using Triaxe experimental protocol, which shows decreasing trend from ∼1750, with intensities during 18th lower than expected geomagnetic models. These new data appear consistent other previously western Europe Russia, when transferred geometry gufm1 model. Together, these used recalibrate moment evolution provided The resulting appears non-linear, clear relative minimum magnitude late illustrate fact that at present can neither be satisfactorily confirmed nor refuted datasets available Eurasia (as well as wider spatial scale), mainly significant dispersion Our interpretation relies accuracy model, less reliable prior ∼1750. Nevertheless, proposed seems true feature behavior.