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Cosmogenic isotopes provide the only quantitative proxy for analyzing thelong-term solar variability over a centennial timescale. While essentialprogress has been achieved in both measurements and modeling of the cosmogenicproxy, uncertainties still remain in the determination of the geomagneticdipole moment evolution. Here we improve the reconstruction of solar activityover the past nine millennia using a multi-proxy approach. We used records ofthe 14C and 10Be cosmogenic isotopes, current numerical models of the isotopeproduction and transport in Earth's atmosphere, and available geomagnetic fieldreconstructions, including a new reconstruction relying on an updatedarcheo-/paleointensity database. The obtained series were analyzed using thesingular spectrum analysis (SSA) method to study the millennial-scale trends. Anew reconstruction of the geomagnetic dipole field moment, GMAG.9k, is builtfor the last nine millennia. New reconstructions of solar activity covering thelast nine millennia, quantified in sunspot numbers, are presented and analyzed.A conservative list of grand minima and maxima is provided. The primarycomponents of the reconstructed solar activity, as determined using the SSAmethod, are different for the series based on 14C and 10Be. These primarycomponents can only be ascribed to long-term changes in the terrestrial systemand not to the Sun. They have been removed from the reconstructed series. Incontrast, the secondary SSA components of the reconstructed solar activity arefound to be dominated by a common ~2400-yr quasi-periodicity, the so-calledHallstatt cycle, in both the 14C and 10Be based series. This Hallstatt cyclethus appears to be related to solar activity. Finally, we show that the grandminima and maxima occurred intermittently over the studied period, withclustering near highs and lows of the Hallstatt cycle, respectively.

Solar activity during the Holocene: the Hallstatt cycle and its consequence for grand minima and maxim