A novel Bayesian approach for disentangling solar and geomagnetic field influences on the radionuclide production rates

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Abstract

Cosmogenic radionuclide records (e.g., 10Be and 14C) contain information on past geomagnetic dipole moment and solar activity changes. Disentangling these signals is challenging, but can be achieved by using independent reconstructions of the geomagnetic dipole moment. Consequently, solar activity reconstructions are directly influenced by the dipole moment uncertainties. Alternatively, the known differences in the rates of change of these two processes can be utilized to separate the signals in the radionuclide data. Previously, frequency filters have been used to separate the effects of the two processes based on the assumption that millennial-scale variations in the radionuclide records are dominated by geomagnetic dipole moment variations, while decadal-to-centennial variations can be attributed to solar activity variations. However, the influences of the two processes likely overlap on centennial timescales and possibly millennial timescales as well, making a simple frequency cut problematic. Here, we present a new Bayesian model that utilizes the knowledge of solar and geomagnetic field variability to reconstruct both solar activity and geomagnetic dipole moment from the radionuclide data at the same time. This method allows for the possibility that solar activity and geomagnetic dipole moment exhibit variations on overlapping timescales. The model was tested and evaluated using synthetic data with realistic noise and then used to reconstruct solar activity and the geomagnetic dipole moment from the 14C production record over the last two millennia. The results agree with reconstructions based on independent geomagnetic field models and with solar activity inferred from the Group Sunspot number. Our Bayesian model also has the potential to be developed further by including additional confounding factors, such as climate influences on the radionuclide records. Graphical Abstract: [Figure not available: see fulltext.]

Original languageEnglish
Article number130
JournalEarth, Planets and Space
Volume74
Issue number1
DOIs
Publication statusPublished - 2022 Dec 1

Subject classification (UKÄ)

  • Geophysics

Keywords

  • C
  • Cosmogenic radionuclide
  • Holocene
  • Paleomagnetism
  • Solar activity

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