Temporal evolution and rigidity dependence of the solar modulation lag of Galactic cosmic rays by Nicola Tomassetti et al. on Tuesday 22 November

When traveling in the heliosphere, Galactic cosmic rays (GCRs) are subjected

to the solar modulation effect, a quasiperiodical change of their intensity

caused by the 11-year cycle of solar activity. Here we investigate the

association of solar activity and cosmic radiation over five solar cycles, from

1965 to 2020, using a collection of multichannel data from neutron monitors,

space missions, and solar observatories. In particular, we focus on the time

lag between the monthly sunspot number and the GCR flux variations. We show

that the modulation lag is subjected to a 22-year periodical variation, ranging

from about 2 to 14 months and following the polarity cycle of the Sun's

magnetic field. We also show that the lag is remarkably decreasing with

increasing energy of the GCR particles. These results reflect the interplay of

basic physics phenomena that cause the GCR modulation effect: the drift motion

of charged particles in the interplanetary magnetic field, the latitudinal

dependence of the solar wind, the energy dependence of their residence time in

the heliosphere. Based on this interpretation, we end up with a global

effective formula for the modulation lag and testable predictions for the flux

evolution of cosmic particles and antiparticles over the solar cycle.

arXiv: http://arxiv.org/abs/http://arxiv.org/abs/2210.05693v2