The Maunder Minimum and the Sun as the Possible Source of Particles Creating Increased Abundance of the 14C Carbon Isotope

Abstract

The Maunder Minimum was the time during the second part of the 17th century, nominally from 1645 to 1717 AD, when unusually low numbers of sunspots were observed. On the basis of numerous recorded observations of auroras in the early 18th century, the end of the Minimum could be regarded as around 1700, but details of sunspot observations by Jan Heweliusz (Heweliusz, Machina Coelestis, 1679), John Flamsteed and Philippe de La Hire in 1684 allow us to interpret the Maunder Minimum as the period without a significant cessation of activity. This Minimum was also recognized in 14 C data from trees which grew during the second part of 17th century.The variation in the production rate of radioactive carbon isotope 14 C is due to modulation of the cosmic ray flux producing it by the changing level of solar activity and solar magnetic flux. Stronger magnetic fields in the solar wind make it more difficult for cosmic rays to reach the Earth, causing a drop in the production rate of 14 C. However, more detailed analyses of 14 C data indicate that the highest isotope abundances do not occur at the time of sunspot minima, as would be expected on the basis of modulation of the cosmic ray flux by the solar magnetic field, but two years after the sunspot number maximum. This time difference (or phase delay) can be accounted for if in fact there are both solar and non-solar cosmic ray contributions. Solar flares could also contribute high-energy particles and produce 14 C and are generally not most frequent at the time of the highest sunspot numbers in the cycle. Solar flares, most frequent about two years after the sunspot maximum, could be the main source of increased 14 C isotope abundance. This idea changes established earlier relations between sunspot number of this time regarded as low and increased abundance of 14 C isotope, and allows us to interpret the Maunder Minimum as a botanical or statistical effect.

Sunspot positions, areas, and group tilt angles for 1611−1631 from observations by Christoph Scheiner

“…There is a large c-shaped black area surrounding a blank-paper region which appears "bright" in contrast to the "dark" surrounding faculae. Rek (2010) seem to argue in a footnote that this region may have been a white-light flare. The textual description of May 2-4, 1625, by Scheiner (1630, p. 208) says the following:…”

Critical Comment on the Article by R. Rek “The Maunder Minimum and the Sun as the Possible Source of Particles Creating Increased Abundance of the 14C Carbon Isotope”

“…A recent article by Rek (2009), called hereafter R09, presents an analysis of radiocarbon 14 C data and its relation to solar activity. Several strong claims were made by R09: i) radiocarbon 14 C is produced not by galactic cosmic rays (GCR) but mostly by particles of solar or magnetospheric origin (e.g., precipitating from radiation belts) or even by auroral electrons via electron capture by nitrogen; ii) precipitation of radiocarbon from the atmosphere to the ground level and absorption by living trees takes place "very quickly," with the deposition time being "certainly less than one year"; iii) Maunder minimum can be interpreted "as the period without a significant cessation of activity" with "a higher level of solar activity.…”

Toward an Investigation of Diversity and Cultivation of Rye (Secale cereale ssp. cereale L.) in Germany: Methodological Insights and First Results from Early Modern Plant Material

“…AD (Table 6 and Figure S1). This segmentation is caused by the Maunder minimum and the Suess effect, both of which had a considerable impact on the 14C content in the atmosphere [72][73][74], obscuring radiocarbon dates of material that dates between 1650 and 1950. As a result, in the case of Wellerholz GVAC_06, the remains of rye can only broadly be dated to between 1637-1954 cal.…”