Proton fluxes measured by the PAMELA experiment from the minimum to the maximum solar activity for the 24th solar cycle

TL;DR

This study presents detailed measurements of galactic cosmic ray protons over a wide energy range during a full solar cycle, providing valuable data to improve heliospheric propagation models.

Contribution

First to analyze proton fluxes over a broad energy range from minimum to maximum solar activity using a single instrument during the 24th cycle.

Findings

Proton intensities vary significantly with solar activity.

Data supports and refines existing propagation models.

Monthly resolution reveals detailed temporal variations.

Abstract

Precise measurements of the time-dependent intensity of the low energy ($<50$ GeV) galactic cosmic rays are fundamental to test and improve the models which describe their propagation inside the heliosphere. Especially, data spanning different solar activity periods, i.e. from minimum to maximum, are needed to achieve comprehensive understanding of such physical phenomenon. The minimum phase between the 23$^{rd}$ and the 24$^{th}$ solar cycles was peculiarly long, extending up to the beginning of 2010 and followed by the maximum phase, reached during early 2014. In this paper, we present proton differential spectra measured from January 2010 to February 2014 by the PAMELA experiment. For the first time the galactic cosmic ray 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 galactic cosmic rays propagation through the heliosphere.