Solar System Collisions with Dense Interstellar Gas Clouds and Radiocarbon Traces of Periods with “Abnormally Low” Solar Modulation of Cosmic Rays

High‐Resolution 10Be and 36Cl Data From the Antarctic Dome Fuji Ice Core (∼100 Years Around 5480 BCE): An Unusual Grand Solar Minimum Occurrence?

“…The 10 Be data of the 5480 BCE series showed an 8−12‐year periodicity, similar to the ∼11‐year periodicity found in the 14 C production rate of this series (Vasil'ev et al., 2019). This periodic variation probably reflects the Schwabe cycle.…”

“…Note that the uncertainty of the random data series might be overestimated since the baseline variation includes the Schwabe cycle itself. A similar cyclic variation in the 5480 BCE event was found in the 14 C production rate after filtering with an 8.6–14.1‐year bandwidth before and after the 5480 BCE event (Figure 3c in Vasil'ev et al., 2019). The ∼11‐year periodicity in both the 10 Be and 14 C data probably reflects the Schwabe cycle, which is commonly associated with the production of both nuclides.…”

“…The 14 C increase in the 5480 BCE event can be explained by a gamma-ray event if the 10 Be data are not synchronously increased with the 36 Cl data. The 14 C production rate during the 5480 BCE event was calculated by Vasil'ev et al (2019), who detected a peak from 5477 BCE to 5469 BCE. However, excluding the 10 Be enhanced period from the ice core data (5470−5455 BCE), the 36 Cl concentration was not significantly increased above the baseline, and also no enhancement of the 36 Cl concentration was observed over 8 years (two continuous 36 Cl data points in Figure 1).…”

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 Miyake, Jull, et al. ( 2017 ) and this study (Figure 3a ).…”

“…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).…”