Abstract
Abstract The solar modulation effect of cosmic rays in the heliosphere is an energy-, time-, and particle-dependent phenomenon that arises from a combination of basic particle transport processes such as diffusion, convection, adiabatic cooling, and drift motion. Making use of a large collection of time-resolved cosmic-ray data from recent space missions, we construct a simple predictive model of solar modulation that depends on direct solar-physics inputs: the number of solar sunspots and the tilt angle of the heliospheric current sheet. Under this framework, we present calculations of cosmic-ray proton spectra, positron/electron and antiproton/proton ratios, and their time dependence in connection with the evolving solar activity. We report evidence for a time lag months, between solar-activity data and cosmic-ray flux measurements in space, which reflects the dynamics of the formation of the modulation region. This result enables us to forecast the cosmic-ray flux near Earth well in advance by monitoring solar activity.
Highlights
In recent years, new-generation experiments of cosmicray (CR) detection have reached an unmatched level of precision that is bringing transformative advances in astroparticle physics (Amato & Blasi 2017; Grenier et al 2015)
These data enable us to the investigation of the CR modulation effect and its dynamical connection with the evolving solar activity
In this Letter, we have reported new calculations of CR modulation based on a physically consistent model that accounts for particle diffusion, drift, convection and adiabatic cooling
Summary
New-generation experiments of cosmicray (CR) detection have reached an unmatched level of precision that is bringing transformative advances in astroparticle physics (Amato & Blasi 2017; Grenier et al 2015). CRs travel through a turbulent magnetized plasma, the solar wind, which significantly reshapes their energy spectra This effect is known to change with time, in connection with the quasi-periodical 11 year evolution of the solar activity and to provoke different effects on CR particles and antiparticles (Potgieter 2013, 2014). Long-duration space experiments PAMELA (on orbit since 2006) and AMS (since 2011) have started releasing a continuous stream of timeresolved data on CR particles and antiparticles (Adriani et al 2013, 2016; Bindi 2017) These measurements add to a large wealth of low-energy data collected in the last decades by space missions CRIS/ACE (Wiedenbeck et al 2009) IMP-7/8 (Garcia-Munoz et al 1997), Ulysses (Heber et al 2009), EPHIN/SOHO (Kuhl et al 2016), and from ground data provided continuously by the neutron monitor (NM) worldwide network (Mavromichalaki et al 2011; Steigies 2015)
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