Charge sign dependence of recurrent Forbush decreases in 2016-2017

This study investigates the periodicities of galactic cosmic ray flux attributed to CIR using Alpha Magnetic Spectrometer (AMS-02) data from late 2016 to early 2017. We determine the rigidity dependence of recurrent Forbush decrease (RFD) amplitudes induced by CIRs for different particles with a focus on charge sign. We carried out a frequency analysis using a Lomb-Scargle algorithm and superposed epoch analysis for all particles. For protons and helium, we compared the results with a single Forbush decrease (FD) analysis. Our results reveal that the rigidity dependence of proton amplitudes attributed to the northern coronal hole is in qualitative agreement with previous findings. In contrast, the amplitudes attributed to the southern coronal hole show no rigidity dependence. Furthermore, the amplitude of the helium modulation exceeds that of protons, in line with the observation for long-term modulation. For positrons, statistical limitations stand in the way of any definitive conclusions. In comparison to the positively charged particles, the modulation behavior of electrons reveals a different pattern.