Volume 610, February 2018
|Number of page(s)||6|
|Published online||19 February 2018|
Long-term evolution of the heliospheric magnetic field inferred from cosmogenic 44Ti activity in meteorites
Istituto Nazionale di Astrofisica, Osservatorio Astrofisico di Torino,
Strada Osservatorio 20,
2 Dipartimento di Fisica, Università di Torino, Via P. Giuria 1, 10125 Torino, Italy
3 Wentworth Institute of Technology, Boston, MA, USA
4 Physical Research Laboratory and Basic Sciences Research Institute, Navrangpura, Ahmedabad, India
Accepted: 17 November 2017
Typical reconstructions of historic heliospheric magnetic field (HMF) BHMF are based on the analysis of the sunspot activity, geomagnetic data or on measurement of cosmogenic isotopes stored in terrestrial reservoirs like trees (14C) and ice cores (10Be). The various reconstructions of BHMF are however discordant both in strength and trend. Cosmogenic isotopes, which are produced by galactic cosmic rays impacting on meteoroids and whose production rate is modulated by the varying HMF convected outward by the solar wind, may offer an alternative tool for the investigation of the HMF in the past centuries. In this work, we aim to evaluate the long-term evolution of BHMF over a period covering the past twenty-two solar cycles by using measurements of the cosmogenic 44Ti activity (τ1∕2 = 59.2 ± 0.6 yr) measured in 20 meteorites which fell between 1766 and 2001. Within the given uncertainties, our result is compatible with a HMF increase from 4.87-0.30+0.24 nT in 1766 to 6.83-0.11+0.13 nT in 2001, thus implying an overall average increment of 1.96-0.35+0.43 nT over 235 years since 1766 reflecting the modern Grand maximum. The BHMF trend thus obtained is then compared with the most recent reconstructions of the near-Earth HMF strength based on geomagnetic, sunspot number, and cosmogenic isotope data.
Key words: Sun: magnetic fields / solar-terrestrial relations / meteorites, meteors, meteoroids
© ESO, 2018
Current usage metrics show cumulative count of Article Views (full-text article views including HTML views, PDF and ePub downloads, according to the available data) and Abstracts Views on Vision4Press platform.
Data correspond to usage on the plateform after 2015. The current usage metrics is available 48-96 hours after online publication and is updated daily on week days.
Initial download of the metrics may take a while.