THE EMPIRICAL MODE DECOMPOSITION TO STUDY THE QUASI-BIENNIAL MODULATION OF SOLAR MAGNETIC ACTIVITY AND SOLAR NEUTRINO FLUX

The time variability of solar activity indices such as sunspot areas (SAs) and green-line coronal emission, fluxes of solar energetic protons and galactic cosmic rays (CRs) in the period 1974–2001 has been investigated through the empirical mode decomposition (EMD). We found that the quasi-biennial periodicity is a prominent time scale of solar variability, having the energetic particle indices an amplitude comparable with the 11 years one. Moreover, we provide evidence for the quasi-biennial modulation of the solar neutrino flux, which results to be also significantly correlated with the fluxes of solar energetic protons and galactic CRs. The significance of all the correlation has been tested by applying both bootstrap and Monte Carlo methods.