Table 1
Magnitude estimations of historical solar events for geomagnetic storms (Dst estimates [nT] with the contemporaneous geomagnetic measurements), solar flares (GOES ABCMX classification defined by soft X-ray (SXR) peak intensity, e.g., X1 = 1.0 × 10−4 [W m−2], Cliver et al., 2022), and SEP events (event-integrated fluence >200 MeV: F200 [cm−2]).
| Event(CE) | Geomagnetic storm (Dst estimate [nT]) | Solar flare (GOES ABCMX SXR classification) | SEP (event-integrated/annual integrated F200 [cm−2]) |
|---|---|---|---|
| 1872 | ~ −834 (Feb.) (Hayakawa et al., 2023b) | NA | <1 × 109* |
| 1859 | < −600 (28 Aug.) (Hayakawa et al., 2022a) | NA | <1 × 109* |
| ≈ −949 ± 30 (2 Sep.) (Hayakawa et al., 2022a) | ~X64.4 ± 7.2 (Cliver et al., 2022); ≈X80 (X46–X126) (Hayakawa et al., 2023a) | ||
| 993 | NA** | NA | 4.7 ± 1.9 × 109 (Usoskin et al., 2023) |
| 774 | NA | X410 ± 200 (single event, Cliver et al., 2020, 2022) | 1.1 ± 0.3 × 1010 (Usoskin et al., 2023) |
Reports for candidate aurorae are confirmed in late 992 to early 993 (Hayakawa et al., 2017a).
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