Selected results of experimental studies of quasi-periodic variations of cosmic rays obtained from ground based measurements, especially from neutron monitor Climax, are reviewed. At high frequencies the dominant periodicity is the solar diurnal variation and its higher harmonics. The slope of power spectrum density at high frequencies is flatter for solar maxima than for solar minima. Wavelet spectra are useful tool for checking the fine strucure of quasi-periodicities and their temporal behaviour. The ~27 day, ~13.5 day and ~9 day quasi-periodicity is far more complex than the diurnal one. For ~27 day variation, two local peaks are temporarily observed, one near 27 and second one near 30-31 days with variable contribution to the signal. ~150 days, ~1.7 yr periodicities are clearly seen in the Lomb-Scargle periodogram.
Kudela, K., Bobik, P., Boella, G., Boschini, M., Consolandi, C., Della Torre, S., et al. (2012). On Quasi-Periodic Variations of Cosmic Rays. In Proceedings of the 13th ICATPP Conference "Astroparticle, Particle, Space Physics and Detectors for Physics Application" (pp.258-265). World Scientific [10.1142/9789814405072_0038].
On Quasi-Periodic Variations of Cosmic Rays
BOELLA, GIULIANO FILIPPO;CONSOLANDI, CRISTINA;GERVASI, MASSIMO;Grandi, D;PENSOTTI, SIMONETTA;TACCONI, MAURO
2012
Abstract
Selected results of experimental studies of quasi-periodic variations of cosmic rays obtained from ground based measurements, especially from neutron monitor Climax, are reviewed. At high frequencies the dominant periodicity is the solar diurnal variation and its higher harmonics. The slope of power spectrum density at high frequencies is flatter for solar maxima than for solar minima. Wavelet spectra are useful tool for checking the fine strucure of quasi-periodicities and their temporal behaviour. The ~27 day, ~13.5 day and ~9 day quasi-periodicity is far more complex than the diurnal one. For ~27 day variation, two local peaks are temporarily observed, one near 27 and second one near 30-31 days with variable contribution to the signal. ~150 days, ~1.7 yr periodicities are clearly seen in the Lomb-Scargle periodogram.
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