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

Owens, M. J. ORCID: https://orcid.org/0000-0003-2061-2453, Cliver, E., McCracken, K. G., Beer, J., Barnard, L. ORCID: https://orcid.org/0000-0001-9876-4612, Lockwood, M. ORCID: https://orcid.org/0000-0002-7397-2172, Rouillard, A., Passos, D., Riley, P., Usoskin, I. and Wang, Y.-M. (2016) Near-Earth heliospheric magnetic field intensity since 1750. Part 2: cosmogenic radionuclide reconstructions. Journal of Geophysical Research: Space Physics, 121 (7). pp. 6064-6074. ISSN 2169-9402 doi: 10.1002/2016JA022550

Abstract/Summary

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.

Item Type	Article
URI	https://reading-clone.eprints-hosting.org/id/eprint/65894
Identification Number/DOI	10.1002/2016JA022550
Refereed	Yes
Divisions	Science > School of Mathematical, Physical and Computational Sciences > Department of Meteorology
Publisher	American Geophysical Union
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