Modulazione degli "scaler data" (esperimento Auger) dovuta all'attività solare

Solar activity and transient events induce variations in the interstellar medium, affecting the magnetic behavior of cosmic-ray particles. Consequently, the flux of low-energy cosmic rays reaching the Earth's atmosphere may reveal solar modulations. The secondary particles, which originate from the interaction of cosmic rays with the atmosphere, can be revealed by an array of ground detectors. In my thesis, I present the analysis of the low-threshold rate (scaler) of cosmic rays time series recorded in 16 years of operation by the surface detectors of the Pierre Auger Observatory in Malargüe (Argentina). These data correspond to the count of particles releasing energy within the range [15-100] MeV, which originate from showers of primary cosmic rays spanning energy between 10 GeV and a few TeV. I focused on revealing the solar activity imprint in this record. Both long-term components, with periods ranging from decades to a few days, and short-term variabilities, with periods as short as a few hours, have been extracted from noise by performing advanced spectral analysis through the Singular Spectrum Analysis (SSA) and the Continuous Wavelet Transform (CWT). In order to study the possible solar origin of the detected modulations, the series have been compared with several solar proxies, namely the number and surface area of sunspots, together with the coronal magnetic field, the absolute value and the radial component of the heliospheric magnetic field.