Figure 1. Correlation between ratio of peak fluxes of flare microwave bursts at 8.8 and 15.4 GHz (parameter S₉/S₁₅) and spectral index of solar proton fluxes (parameter δ=lg(J₁₀/J₁₀₀) calculated by measurements near the Earth in the >10 MeV and >100 MeV channels. Proton events of 1987-2008, associated with flares on the western half of the disk, are considered. The straight line corresponds to the linear regression. Events, in which a ground level enhancement (GLE) took place, are designated by crosses. The following events are marked by numbers (numeration according to Main Table): 41 - 14.07.2000, 43 - 12.09.2000, 59 - 26.12.2001, 63 - 15.07.2002, 81 - 20.01.2005.