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In this study, daily cosmic ray data obtained with the KACST muon detector for the period 2002–2012 were analyzed for quasi-periodicities. Power-spectrum analysis was carried out and several periodicities were identified. The results reveal several periodicities at different frequency scales: 817 days (~2.19 years), 617 days (~1.7 years), 475 days (~1.3 years), 421 days (1.15 years), 290 days (~0.8 years), 227 days (~0.62 years), 185 days (~0.52 years), 153 days, 135 days, 120 days, 93 days, 84 days, 73 days, 65 days, 53–45 days, 38 days, 31 days, 25–27 days, 21 days and 13 days. The obtained periodicities are in an agreement with those previously reported by several investigators. The identified periodicities have strong relevance to solar activity parameters such as variations in the interplanetary magnetic field. In comparison, the data from two neutron monitors (NMs), Lomnický stit and Oulu NMs, for the same period were used and their power spectra were correspondingly obtained. Similarities and differences in the position of the cosmic-ray peaks measured by the KACST muon detector and by the two NMs have been presented and discussed. While most of the periodicities reported by the muon detector are also found in the NM data, the ~1.7-yr variation is not found. Instead, a shift of 1.6–1.8 years in the NM data is observed which may be due to the limited epoch considered in this study.

In October 2017, a multi-layer small multi-wire (MW) detector for cosmic ray (CR) muon measurements was installed at King Abdulaziz City for Science and Technology (KACST), Riyadh, Saudi Arabia (Rc = 14.4 GV). This detector is considered to be the first of its kind used for long term CR measurements. In this study, CR data collected from KACST-MW detection system and radiosonde measurements were used to investigate the effect of atmospheric pressure, ground temperature, height of the muon production layer, temperature at that layer, and temperature weighted by atmospheric mass, on CR muons. Regression analyses between the observed muon count rate and these variables were carried out and the corresponding coefficients were obtained and used to correct the observed muon count rate for the temporal variation of these variables. The effect of the atmospheric pressure was conducted first and used to correct the data for this effect. The pressure corrected count rate is anti-correlated with the height of muon production, ground temperature, and atmospheric mass-weighted temperature. On the other hand, the temperature at the muon production layer is positively correlated with the muon count rate. The obtained results from this study are in good agreement with those reported by several researchers. Taking advantages of the relationship between the detected CR muons and the temperature at the muon production layer (stratospheric temperature), this relationship is inverted to calculate this temperature from muon observations. The proposed technique provides excellent predictability of the stratospheric temperatures.

On January 20, 2005, 7:02–7:05 UT the Aragats Multidirectional Muon Monitor (AMMM) located at 3200 m a.s.l. registered enhancement of the high energy secondary muon flux (threshold ∼5 GeV). The enhancement, lasting for 3 min, has statistical significance of ∼4 σ and is related to the X7.1 flare seen by the GOES, and very fast (>2500 km/s) CME seen by SOHO, and the Ground Level Enhancements (GLE) #69 detected by the world-wide network of neutron monitors and muon detectors. The energetic and temporal characteristics of the muon signal from the AMMM are compared with the characteristics of other monitors located at the Aragats Space-Environmental Center (ASEC) and with other neutron and muon detectors. Since secondary muons with energies >5 GeV are corresponding to solar proton primaries with energies 20–30 GeV we conclude that in the episode of the particle acceleration at 7:02–7:05 UT 20 January 2005 solar protons were accelerated up to energies in excess of 20 GeV.