“…Unlike the GCR model, which simply modifies a well-defined primary spectrum using a single modulation parameter, there is no single spectral shape that can be applied to all GLEs. Attempts to characterize the spectral shape of GLEs have taken various forms, including Weibull functions (Dyer & Lei, 2001;Dyer et al, 2003), double-power-law "Band" functions (Asvestari et al, 2017;Atwell et al, 2011;Band et al, 1993;Tylka & Dietrich, 2009), and modified power-laws (Jiggens et al, 2019;Mishev et al, 2014;Mishev & Usoskin, 2016). These may be parameterized as functions of energy or rigidity, but the essential difference remains the slope of the spectra (spectral index) in the region of interest for atmospheric radiation effects-that is, particle rigidities from ∼1 GV to >10 GV.…”