Radiocarbon Production Events and their Potential Relationship with the Schwabe Cycle

Abstract

Extreme cosmic radiation events occurred in the years 774/5 and 993/4 CE, as revealed by anomalies in the concentration of radiocarbon in known-age tree-rings. Most hypotheses point towards intense solar storms as the cause for these events, although little direct experimental support for this claim has thus far come to light. In this study, we perform very high-precision accelerator mass spectrometry (AMS) measurements on dendrochronological tree-rings spanning the years of the events of interest, as well as the Carrington Event of 1859 CE, which is recognized as an extreme solar storm even though it did not generate an anomalous radiocarbon signature. Our data, comprising 169 new and previously published measurements, appear to delineate the modulation of radiocarbon production due to the Schwabe (11-year) solar cycle. Moreover, they suggest that all three events occurred around the maximum of the solar cycle, adding experimental support for a common solar origin.

A Single‐Year Cosmic Ray Event at 5410 BCE Registered in 14C of Tree Rings

“…During the gradual decay-phase of the event, there are no rapid changes in Δ 14 C, only rather small regular fluctuations which might be caused by the Schwabe cycle. Since other studies successfully applied a bandpass filter to detect the Schwabe cycle in 14 C ring records (e.g., Güttler et al, 2013;Scifo et al, 2019;Vasil'ev et al, 2019), we used a similar approach (6-25 year bandpass analysis) for the period of 5491 BCE to 5371 BCE using data from and this study (Figure 3a). First, to subtract the effect of the 5410 BCE event, we fitted the Δ 14 C data from 5414 to 5396 BCE by using a 22-box carbon cycle model (Büntgen et al, 2018) assuming a pulsed 14 C production with 4.6 × 10 26 atoms occurred in 5410 BCE (Figure S4).…”

“…The Schwabe cycle manifested in the Δ 14 C data is expected to lag the actual solar cycle by 2-3 years because of the large and exchanging carbon reservoirs in the carbon cycle (e.g., Siegenthaler et al, 1980). For example, a 3 ± 1 year lag was observed in the recent verification of sunspot fluctuations around the 1860s using tree-ring 14 C data (Scifo et al, 2019). The 5410 BCE event occurred during a solar maximum which, considering this 3-year lag, is likewise consistent with the results of the 774/775 and 992/993 CE SEP events (Scifo et al, 2019).…”

The European Beech Annual Tree Ring Widths Time Series, Solar–Climatic Relationships and Solar Dynamo Regime Changes

“…It should be noted in this course that the "amplitude" Gnevishev-Ohl' s rule [73] according to which the amplitudes of even numbered solar cycles is weaker as the followed them odd numbered ones is valid in the whole period of sunspot cycles SC10-SC21, i.e., between 1856-1986 AD. On the other hand, the integral sunspot activity during the even numbered cycles is smaller as in the followed odd numbered ones (the "classical" Gnevishev-Ohl's rule [74]) for the whole period 1810-1986 AD, i.e., since SC5. The 20-22 year cycle the existence in atmospheric circulation (and "Brown effect") over North Atlantic and Europe during the 19th and 20th centuries is probably caused in high degree by the Gnevishev-Ohl's rule effect.…”

Solar system exposure to supernova γ radiation

“…In conclusion, the presented data and analysis do not rule out solar flare or solar activity hypotheses (Usoskin et al ., 2013; Jull et al ., 2018; Scifo et al ., 2019) for rapid-onset 14 C increases. However, SNe causation instead is viable for many of them.…”