Analysis of Cosmic Rays' Atmospheric Effects and Their Relationships to Cutoff Rigidity and Zenith Angle Using Global Muon Detector Network Data

Abstract

Cosmic rays are charged particles whose flux observed at Earth shows temporal variations related to space weather phenomena and may be an important tool to study them. The cosmic ray intensity recorded with ground-based detectors also shows temporal variations arising from atmospheric variations. In the case of muon detectors, the main atmospheric effects are related to pressure and temperature changes. In this work, we analyze both effects using data recorded by the Global Muon Detector Network, consisting of four multidirectional muon detectors at different locations, in the period between 2007 and 2016. For each Global Muon Detector Network directional channel, we obtain coefficients that describe the pressure and temperature effects. We then analyze how these coefficients can be related to the geomagnetic cutoff rigidity and zenith angle associated with cosmic ray particles observed by each channel. In the pressure effect analysis, we found that the observed barometric coefficients show a very clear logarithmic correlation with the cutoff rigidity divided by the zenith angle cosine. On the other hand, the temperature coefficients show a good logarithmic correlation with the product of the cutoff and zenith angle cosine after adding a term proportional to the sine of geographical latitude of the observation site. This additional term implies that the temperature effect measured in the Northern Hemisphere detectors is stronger than that observed in the Southern Hemisphere. The physical origin of this term and of the good correlations found in this analysis should be studied in detail in future works.

Atmospheric Temperature Effect in Secondary Cosmic Rays Observed With a 2 m2 Ground‐Based tRPC Detector

“…variations due to the temperature effect are approximated by where x ( h i ) is the atmospheric depth at the same altitude. Indeed, a very recent study from the GMDN (Mendonça et al., 2019) found a relation between the mass‐weighted temperature coefficient and the cutoff rigidity ( R c ) and latitude ( L ) for vertical incidence: …”

Atmospheric Temperature Effect in secondary cosmic rays observed with a two square meter ground-based detector

“…Here the temperature coefficient α T and the effective temperature T ef f are defined as Theoretical (Dmitrieva et al, 2011) This work ∆α α T (%/K) -0.319 -0.279 ± 0.051 0.040 ± 0.051 (Mendonça et al, 2019) This work ∆α α M SS (%/K) -0.271 -0.233 ± 0.045 0.038 ± 0.045…”

“…where x(h i ) is the atmospheric depth at the same altitude. Indeed, a very recent study from the GMDN (Mendonça et al, 2019) found a relation between the mass-weighted temperature coefficient and the cutoff rigidity (R c ) and latitude (L) for vertical incidence:…”

MITO: a new directional muon telescope

“…There are 6 Â 6 in the first, 4 Â 4 in the second and 4 Â 9 individual detectors in the third. On the other hand, the Kuwait telescope is composed of four 5 Â 5 m layers (0.8 m apart) of cylindrical proportional counter tubes below a lead layer (Mendonça et al, 2019). When a coincidence is registered between two detectors, one at each layer, the trajectory of a particle can be determined.…”