tokens: applied to the data of the Apatity Neutron Monitor ( http://www.nmdb.eu/nest/search.php/ ); the results, reported in the third panel of Figure 3 , show a periodicity that seems to coincide with the observed one by PAMELA. To try to explore the origin of this quasi-periodicity, a raw periodgram (95% Kolmogorov–Smirnov confidence level) of the first two rigidity spectra, 0.4–0.65 GV and 0.65–15 GV, has been carried out. The results are presented in the fifth panel of Figure 3 . Peaks appear around 580, 450, 370, 320, and 230 days. The 580-day periodicity is possibly linked to an ∼600-day periodicity reported in Valdés-Galicia et al. ( 1996 ), which could be associated with fluctuations in the southern coronal hole area and in large active regions. The seasonal ∼370-day cosmic-ray variation is caused by the Earth’s rotation (Forbush 1954 ). The 230-day peak was also found in El-Borie et al. ( 2011 ) as a 0.7-year periodicity during the A > 0 solar cycle (1992–2000). The last periodicity, ∼450 days, was already described in Valdés-Galicia et al. ( 1996 ) as a possible 1.2-year periodicity but its origin is not reported. The nature of the ∼450-day periodicity could be related to quasi biennial oscillations or QBOs (Vecchio et al. 2012 ; Laurenza et al. 2012 ). QBOs have been detected as a prominent scale of variability in GCRs, but they could just be more an effect of superposition of other periodic/quasi-periodic processes and not stochastic perturbations. Higher QBOs have been observed during solar maxima with respect to solar minima (Bazilevskaya et al. 2015 ); this could explain a higher signal in the descending phase of PAMELA proton data (see Figure 1 ) and could be related to different drift effects in different polarities of the HMF. In the past, numerous periodicities between 0.5 and 4 years have been correlated to QBOs (Kato et al. 2003 ; Rybák et al. 2001 ; Kudela et al. 2002 , 2010 ; Benevolenskaya ( 1998 ) and it is very difficult to disentangle their effects from others. In this work, a different hypothesis is proposed for the 450-day periodicity as a study case: a Jovian origin, more exotic but largely proposed in the past. It is well known that the planet Jupiter possesses a very intense magnetosphere due to the combination between its strong magnetic field, about 10 4 times larger than that of the Earth, and the weakness of the solar wind at 5 au. Evidence that Jupiter could generate high-energy particles has been shown for electrons (Teegarden et al. 1974 ; Simpson et al. 1974 ), and more recent studies revealed that the impulsive and quasi-periodic bursts observed in Jupiter’s duskside magnetosphere also contain protons and helium nuclei in the range 0.7–10 MeV/nucleon (Zhang et al. 1995 ). Moreover, an indication that acceleration mechanisms can operate in magnetospheric environments has been found on Earth, where trapped particles are shown to be accelerated to relativistic energies by local acceleration acting in the heart
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