Cosmic ray solar modulation limit: validation of empirical simplification for forbush decrease

e-converted-space"> method to reconstruct the time variation of the Galactic Cosmic Ray (GCR) modulation potential, Δφ. ES against conventional methods reported in the literature (in particular we reproduced the modulation potential obtained by Ghelfi et al. 2016 and Usoskin et al. 2017) ES method to estimate the time evolution of the GCR Proton and Helium spectra during a Forbush Decrease (FD) observed recently. We this, we were able to compute the threshold of maximum energy (i. e. the modulation limit) at which the GCR spectrum experiences modulation (a change of one percent) during the FD main phase. This limit depends of the intensity of the solar wind disturbance and is in the range of 50 to 150 GeV.