Table 1 Summary of all the Grand Solar Minima identified by single-year 14C measurements15,16 and the four new candidates found in this study (values shown in bold)

From: Patterns in solar activity over the first millennium CE

Grand Solar Minima

Peak rise in Δ14C

Φ (MeV)

Duration (yrs)

Dalton (1797–1823 CE)

10.62 ± 2.65‰

327–347

26

Maunder (1621–1718 CE)

21.32 ± 2.48‰

220–320

97

Spörer (1388–1558 CE)

26.22 ± 2.72‰

215–305

170

Wolf (1279–1349 CE)

14.55 ± 2.81‰

273–361

70

Oort (1021–1060 CE)

15.29 ± 2.01‰

332–381

39

Horrebow (640–730 CE)

19.96  ± 2.41‰

188–252

90

400–450 CE

13.45  ± 1.86‰

237–318

40

200–280 CE

17.49  ± 2.22‰

246–317

80

105–150 CE

11.76  ± 2.11‰

302–404

45

Platonic (413–325 BCE)

25.54 ± 2.48‰

296–352

88

Homeric (833–705 BCE)

24.11 ± 2.38‰

258–277

128

  1. The peak rise in Δ14C is defined as the start and end point of its continuous increase during the GSM period. The uncertainties in the peak rise in Δ14C are estimated by the propagation of the measurement errors of the corresponding years. The duration of GSM proposed in this study is obtained by identifying when the solar modulation parameter (Φ) starts to decrease and when it returns to the level evident before the decrease. In both Brehm et al. studies15,16, they used the Local Interstellar Spectrum (LIS) Model built by Herbst et al.43, while this study applied the LIS model used in Kovaltsov et al.44. To ensure the computed Φ is comparable, we applied the linear conversion proposed by Herbst et al.43 to the results from Brehm et al.15,16. The conversion formula is: ΦBrehm = 1.025 ⋅ Φthis study + 24.18.
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