Abstract

In April 2017, a mini neutron monitor (NM) was installed at King Abdulaziz City for Science and Technology (KACST) central Saudi Arabia (Riyadh; cut-off rigidity, Rc = 14.4 Gv) for continuous observation of the cosmic ray (CR) neutrons. The detector was built as a major aspect of the international scientific joint effort between the Centre of Space Research (North-West University, Potchefstroom, South Africa) and KACST. The recorded data correspond to low energy neutrons that primarily have energies lower than 20 GeV. In this paper, a brief description about the mini NM detector will be given. The influence of atmospheric pressure on the recorded CR neutrons was studied and the barometric coefficient was calculated and used to eliminate the pressure effects from the measured data. The obtained coefficient was consistent with those previously obtained by several investigators. The daily variation of the CR neutron was studied and characterized. Short-term CR periodicities, such as the 27-day period, and its two harmonics, were identified. The obtained periodicities are in agreement with those reported by different researchers. The obtained results from this detector have been compared to the existing 1 m2 scintillator detector showing comparable results. Long-term data from this detector will be of incredible significance to the research community to investigate several types of CR variations resulting from solar activity at such high cut off rigidity site.

Highlights

  • Atmospheric pressure is the most effective atmospheric variable influencing the flux of the secondary cosmic ray (CR) particles (e.g., Dorman 2004)

  • Cosmic ray neutrons represent the low energy part of the extensive air shower produced in the atmosphere by the interactions between the primary CRs and atmospheric molecules

  • It was found that the atmospheric pressure is anti-correlated with the CR data

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Summary

Introduction

Cosmic rays (CRs) are energetic charged particles originating from deep spaces that reach the top of our atmosphere about 30 km above the Earth’s surface. Solar disturbances change the energy output from the sun, which affects the interplanetary medium and the terrestrial environment [13] These variations affect the propagation of the high-energy CR in the heliosphere, and their rate at the top of the atmosphere is modulated [14] [15]. Since their discovery by Viktor Hess in 1912, different types of space-based and ground-level CR detectors have been developed to study the CR modulations in different time scales [16] [17] These detectors were sensitive to various components of CRs. Because of its high cut off rigidity and unique location [18] [19] [20] [21], monitoring CR variations in Saudi Arabia is of an incredible significance for the research community.

Concept of Neutron Monitors
KACST Mini Neutron Monitor
Pressure Corrections
Diurnal Variations
Short Term Periodicities
Conclusions
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