New source spectrum alongside that by Ferreira et al. (2001) in orange and the suggestion by Haasbroek et al. (1997; green) as discussed in Sect. 4. In the upper panel all three spectra are shown alongside the Jovian flyby data and the 1 σ error region surrounding our estimation. The lower panel shows the relative deviation of the estimations, calculated as (j_previous− j_new)∕j_new. Especially inthe energy range above E_break = 9.4 MeV the lower panel shows how the deviation increases up to over 100% and even far more for the spectrum by Ferreira et al. (2001).