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Near-Earth heliospheric magnetic field intensity since 1750: 2. Cosmogenic radionuclide reconstructions

Abstract : This is Part 2 of a study of the near-Earth heliospheric magnetic field strength, B, since 1750. Part 1 produced composite estimates of B from geomagnetic and sunspot data over the period 1750-2013. Sunspot-based reconstructions can be extended back to 1610, but the paleocosmic ray (PCR) record is the only data set capable of providing a record of solar activity on millennial timescales. The process for converting 10Be concentrations measured in ice cores to B is more complex than with geomagnetic and sunspot data, and the uncertainties in B derived from cosmogenic nuclides (~20% for any individual year) are much larger. Within this level of uncertainty, we find reasonable overall agreement between PCR-based B and the geomagnetic- and sunspot number-based series. This agreement was enhanced by excising low values in PCR-based B attributed to high-energy solar proton events. Other discordant intervals, with as yet unspecified causes remain included in our analysis. Comparison of 3 year averages centered on sunspot minimum yields reasonable agreement between the three estimates, providing a means to investigate the long-term changes in the heliospheric magnetic field into the past even without a means to remove solar proton events from the records.
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Submitted on : Tuesday, May 17, 2022 - 8:57:06 AM
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JGR Space Physics - 2016 - Owe...
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M. J. Owens, E. Cliver, K. G. Mccracken, J. Beer, L. Barnard, et al.. Near-Earth heliospheric magnetic field intensity since 1750: 2. Cosmogenic radionuclide reconstructions. Journal of Geophysical Research: Space Physics, 2016, 121, pp.6064-6074. ⟨10.1002/2016JA022550⟩. ⟨insu-03669464⟩



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