Solar flare SXR peak flux cumulative occurrence rate (per year). The blue histogram represents the GOES data from NOAA (1975 – 2017) – see Section A.1. Green dashed and blue dotted lines denote different extrapolations: power law (ν = 41.95 × (I/I₀)^−1.162 [yr⁻¹]) and Weibull (ν = 41.95 × exp( − 10.2 ⋅ (I^k + I₀^k)/I₀^k) [yr⁻¹], where I₀ = 4.29⋅10⁻⁵ W/m², k = 0.104), respectively, according to Sakurai (2023, – S23).