Behaviour of 27-Day and 13.5-Day Periodicities in Galactic Cosmic Particles as Observed by Spacecraft and Neutron Monitors During Different Solar Polarity Cycles

Abstract An analysis has been made of the behaviour 27-day and 13.5-day periodicities in proton, C, O galactic-cosmic-ray (GCR) particles at different energies as observed by Advanced Composition Explorer (ACE) SOHO ( Solar Heliospheric Observatory ) spacecraft during both Cycles 23 24. In addition, periods solar-wind-modulation parameter $\zeta $ ζ = B IMF × V SW investigated same time interval to determine existence a possible solar-polarity dependence. Ground-based neutron-monitor (NM) observations, corresponding rigidity cutoff [R C ] parameters, were also studied temporal 24, revealing statistically significant correlation. The Lomb–Scargle periodogram technique employed extract spectral information from above-mentioned observations for each individual year 2001 – 2009 (Cycle 23) 2010 2019 24). Daily mean energetic ACE particle measurements are used identify how vary these cycles function energy. This galactic-cosmic-particle data revealed that stronger minimum Cycle 24/25 when A > 0 (solar dipole pointing North) comparison 23/24 < South) certain energy levels. showed particularly strong energy-dependent periodicities. article reports first an annual time- daily-mean galactic cosmic ground-based neutron monitors consecutive opposite solar-magnetic-field orientations. Periodicity heliospheric solar-wind corroborate results general.