Space Physics, North-West University, Potchefstroom, South Africa
Periodicities in galactic cosmic particles like C, N, O and Fe as observed by the ACE satellite between 2000 and 2019 have been analyzed using various spectral analysis techniques. Daily mean energetic particle measurements are used to identify how several harmonics of the ~ 27-day synodic rotation period change during each individual year. Lomb-Scargle and Morlet wavelet spectral analysis of galactic cosmic particle data at different energies revealed in particular that the fourth harmonic (~7-day) of the solar rotation period occurs exceptionally strong during the minimum of solar cycle 23 (2008, 2009) when A< 0 (solar dipole pointing South) in comparison to the minimum of cycle 24 (2018,2019) when A> 0 (solar dipole pointing North). The results obtained in this investigation showed that galactic cosmic particles as observed by the ACE satellite exhibit peculiar short-term periodicity behaviour as a result of solar polarity dependent magnetic drifts during a negative minimum which is in line with previous results using neutron monitor data from Hermanus and Jungfraujoch (P Kotzé, Solar Physics, 2020).
Spectral analysis, Lomb-Scargle, wavelets, galactic cosmic particles, solar cycle