Reconstructions of the heliospheric modulation potential and Wolf numbers based on the content of the 14C isotope in tree rings during the Maunder and Spörer minimums

Abstract

Data on variations in the content of the 14C cosmogenic isotope in tree rings and the Earth’s atmosphere (Δ¹⁴C) make it possible to study the behavior of solar activity (SA) in previous centuries and millenniums. The latter is related to the fact that SA temporal variations result in a change in the IMF (Interplanetary Magnetic Field) parameters and, as a consequence, in the galactic cosmic ray (GCR) flux, under the action of which the ¹⁴C isotope is produced in the Earth’s atmosphere. This makes it possible to study SA history based on data on the ¹⁴C isotope content in tree rings. However, in this case we have several difficulties related to climate change. Climate changes result in carbon redistribution between natural reservoirs, which is reflected in radiocarbon data and results in solar signal distortion. The effect of variations in the global temperature and carbon dioxide concentration on the reconstruction of the heliospheric modulation potential and Wolf numbers from the late 14th century to the early 19th century is considered. It has been shown that the radiocarbon data do not make it possible to conclude that SA during the Maunder minimum was extremely low as compared to SA during the Dalton minimum.