Precise measurements of the time-dependent intensity of the low-energy (<50 GeV) galactic cosmic rays (GCRs) are fundamental to test and improve the models that describe their propagation inside the heliosphere. In particular, data spanning different solar activity periods, i.e., from minimum to maximum, are needed to achieve comprehensive understanding of such physical phenomena. The minimum phase between solar cycles 23 and 24 was peculiarly long, extending up to the beginning of 2010 and followed by the maximum phase, reached during early 2014. In this Letter, we present proton differential spectra measured from 2010 January to 2014 February by the PAMELA experiment. For the first time the GCR proton intensity was studied over a wide energy range (0.08–50 GeV) by a single apparatus from a minimum to a maximum period of solar activity. The large statistics allowed the time variation to be investigated on a nearly monthly basis. Data were compared and interpreted in the context of a state-of-the-art three-dimensional model describing the GCRs propagation through the heliosphere.

A new generation magnetic spectrometer in space will open the opportunity to investigate the frontiers in direct high-energy cosmic ray measurements and to precisely measure the amount of the rare antimatter component in cosmic rays beyond the reach of current missions. We propose the concept for an Antimatter Large Acceptance Detector In Orbit (ALADInO), designed to take over the legacy of direct measurements of cosmic rays in space performed by PAMELA and AMS-02. ALADInO features technological solutions conceived to overcome the current limitations of magnetic spectrometers in space with a layout that provides an acceptance larger than 10 m${}^2$ sr. A superconducting magnet coupled to precision tracking and time-of-flight systems can provide the required matter–antimatter separation capabilities and rigidity measurement resolution with a Maximum Detectable Rigidity better than 20 TV. The inner 3D-imaging deep calorimeter, designed to maximize the isotropic acceptance of particles, allows for the measurement of cosmic rays up to PeV energies with accurate energy resolution to precisely measure features in the cosmic ray spectra. The operations of ALADInO in the Sun–Earth L2 Lagrangian point for at least 5 years would enable unique revolutionary observations with groundbreaking discovery potentials in the field of astroparticle physics by precision measurements of electrons, positrons, and antiprotons up to 10 TeV and of nuclear cosmic rays up to PeV energies, and by the possible unambiguous detection and measurement of low-energy antideuteron and antihelium components in cosmic rays.

The PAMELA space experiment, in orbit since 2006, has measured cosmic rays (CRs) through the most recent period of minimum solar activity with the magnetic field polarity as A < 0. During this entire time, galactic electrons and protons have been detected down to 70 MV and 400 MV, respectively, and their differential variation in intensity with time has been monitored with unprecedented accuracy. These observations are used to show how differently electrons and protons responded to the quiet modulation conditions that prevailed from 2006 to 2009. It is well known that particle drifts, as one of four major mechanisms for the solar modulation of CRs, cause charge-sign-dependent solar modulation. Periods of minimum solar activity provide optimal conditions in which to study these drift effects. The observed behavior is compared to the solutions of a three-dimensional model for CRs in the heliosphere, including drifts. The numerical results confirm that the difference in the evolution of electron and proton spectra during the last prolonged solar minimum is attributed to a large extent to particle drifts. We therefore present new evidence of charge-sign-dependent solar modulation, with a perspective on its peculiarities for the observed period from 2006 to 2009.

Multimessenger astrophysics is based on the detection, with the highest possible accuracy, of the cosmic radiation. During the last 20 years, the advent space-borne magnetic spectrometers in space (AMS-01, Pamela, AMS-02), able to measure the charged cosmic radiation separating matter from antimatter, and to provide accurate measurement of the rarest components of Cosmic Rays (CRs) to the highest possible energies, have become possible, together with the ultra-precise measurement of ordinary CRs. These developments started the era of precision Cosmic Ray physics providing access to a rich program of high-energy astrophysics addressing fundamental questions like matter-antimatter asymmetry, indirect detection for Dark Matter and the detailed study of origin, acceleration and propagation of CRs and their interactions with the interstellar medium.In this paper we address the above-mentioned scientific questions, in the context of a second generation, large acceptance, superconducting magnetic spectrometer proposed as mission in the context of the European Space Agency’s Voyage2050 long-term plan: the Antimatter Large Acceptance Detector In Orbit (ALADInO) would extend by about two orders of magnitude in energy and flux sensitivity the separation between charged particles/anti-particles, making it uniquely suited for addressing and potentially solving some of the most puzzling issues of modern cosmology.

Spacecraft observations of cosmic ray antimatter intensities can potentially shed new light on previously unknown physics and hence play an essential role in the search for dark matter. At lower energies, however, these particles experience considerable modulation in the heliosphere. Since the advent of cosmic ray modulation studies, simplified approaches to solving the Parker transport equation have been used to glean insights from observations as to the behavior of these particles. We show, due to the inherent limitations imposed by the assumptions made in simplifying the Parker equation, that the use of these approaches can introduce unknown uncertainties into analyses based on them, and thus that these approaches should be used with caution, especially when novel insights into potentially new physics are sought.

The CALorimetric Electron Telescope primary detector (CALET-CAL) is a 30 radiation-length-deep hybrid calorimeter designed for the accurate measurement of high-energy cosmic rays. It is capable of triggering on and giving near complete containment of electromagnetic showers from primary electrons and gamma rays from 1 GeV to over 10 TeV. The first 24 months of on-orbit scientific data (2015 November 01–2017 October 31) provide valuable characterization of the performance of the calorimeter based on analyses of the gamma-ray data set in general and bright point sources in particular. We describe the gamma-ray analysis, the expected performance of the calorimeter based on Monte Carlo simulations, the agreement of the flight data with the simulated results, and the outlook for long-term gamma-ray observations with the CAL.