Evidences of high energy protons with energies beyond 0.4 GeV in the solar particle spectrum as responsible for the cosmic rays solar diurnal anisotropy

TL;DR

This study provides evidence that high-energy solar protons above 0.4 GeV influence cosmic ray muon daily variations, suggesting solar particle energies extend beyond 1 GeV and impact cosmic ray anisotropy.

Contribution

It demonstrates the role of high-energy solar protons in cosmic ray muon variations, offering a new explanation for solar diurnal anisotropy based on observational data.

Findings

High muon intensity correlates with interplanetary magnetic field lines overtake the Earth.

Solar protons contribute to muon flux at energies beyond 1 GeV.

The proposed model explains the solar daily variation more accurately than previous assumptions.

Abstract

Analysis on the daily variations of cosmic ray muons with $E_{\mu}\geq 0.2 GeV$ based on the data of two directional muon telescopes at sea level and with a rigidity of response to cosmic proton spectrum above 0.4 GV is presented. The analysis covers two months of observations and in 60% of days, abrupt transitions between a low to a high muon intensity and vice-verse is observed, the period of high muon intensity is from $\sim 8.0h$ up to $\sim 19.0h$ (local time) and coincides with the period when the interplanetary magnetic field (IMF) lines overtake the Earth. This behavior strongly suggest that the high muon intensity is due to a contribution of solar protons (ions) on the muon intensity produced by the galactic cosmic rays, responsible for the low muon intensity. This implies that the solar particle spectrum extends to energies beyond 1 GeV. We show that this picture can explain the solar daily variation origin, and it is a most accurate scenario than the assumption of corotating galactic cosmic ray with the IMF lines, specially in the high rigidity region. Obtained results are consistent with the data reported in others papers. Some aspects on the sensitivity of our muon telescopes are also presented.