This paper presents the results of the analysis of experimental data obtained at the ground-based experimental complex in the area of CASLEO astronomical complex (Argentina) in the period from June 1 to December 31, 2015, which was developed within the international cooperation between the Lebedev Physical Institute and Mackenzie Presbyterian University (Brazil), as well as the CASLEO astronomical complex. The main attention is paid to the study of variations in the charged and neutral components of cosmic rays and the surface electric field during seismic activity manifestations, i.e., earthquakes in the CASLEO location area. The data on solar activity, the state of interplanetary medium and geomagnetic activity are also used.

This paper provides a brief description individual elements that can be included in the Solntse–Terahertz scientific apparatus that was designed for the first time to carry out an extra-atmospheric experiment onboard the International Space Station . Its purpose is to measure terahertz electromagnetic radiation both from the quiet Sun and during active processes on the Sun (solar flares, coronal mass ejections, etc.), which is necessary to establish the physical nature of solar activity and solar flares. The possibility is discussed of using optoacoustic converters (Golay cells) as receivers of terahertz radiation, the sensitivity, stability, and response time of which were determined in the course of preliminary laboratory studies under terrestrial conditions.

In 2017 CARPET cosmic ray detector was installed at KACST (King Abulaziz City for Science and Technology) at Riyadh (latitude 24.67, longitude 46.74; alt. 613 m; geomagnetic cuttoff rigidity R-c = 14.4 GV) Saudi Arabia. The detector was built as part of the international scientific collaboration between the P.N. Lebedev Physical Institute (LPI, Moscow, Russia) and KACST. The CARPET is sensitive to the low energy secondary component of the cosmic rays (CR). The main goal of this detector is to measure and study the CR variations and investigate their correlations with solar activity and atmospheric phenomena (e.g. thundercloud activity, thunderstorms, etc.). The detector performance was tested and showed comparable results to our existing 1 m(2) scintillator and multiwire detectors. In this paper a brief description of this instrument will be given. Correlation analyses between the CARPET data and atmospheric variables will be carried out and established. Short term periodicities of the CR recorded by CARPET were investigated and recognized. The obtained periodicities are in agreement with those reported by different researchers. Long-term data from CARPET can be a useful tool to investigate several types of CR variations resulting from solar activity or atmospheric processes.

Since their discoveries different types of radiation detectors, sensitive to various components of cosmic rays (CRs) have been developed to monitor and study their variations. As part of the King Abdulaziz City for Science and Technology (KACST) space research program and radiation detector laboratory activities, a CARPET detector was installed at KACST central Saudi Arabia (Riyadh; lat. 24 43; long. 46 40; alt. 613 m; R-c =14.4 GV) for monitoring and exploring the variations of the CRs and their possible correlations with environment variables such as thunderstorms. The detector was designed and built by the Lebedev Physical Institute of the Russian Academy of Sciences (LPI, Moscow, Russia) within an international scientific cooperation between the LPI and the KACST and has been in operation since April 2016. In this paper, the technical aspects of this detector will be briefly discussed. Preliminary results obtained from this detector will be presented and discussed.

A hardware and software system created at the Lebedev Physical Institute and featuring neutron detectors based on SNM-18 neutron counters is described. Its characteristics and the results from a preliminary analysis of data obtained in terrestrial measurements of neutron fluxes in the period 2015–2018 are presented.

The results are presented from an analysis of data on solar activity and cosmic ray variations observed in September 2017. This period is characterized by a sharp increase in the solar flare activity in the active region AR 12673 during the late descending phase of the 24th solar activity cycle. Solar protons are recorded by the particle instruments aboard the GOES-13 satellite, in the atmosphere, and by the ground-based neutron monitor network. A moderate Forbush decrease in the cosmic ray flux during September 6–10 is also recorded by a number of neutron monitors. Several solar proton energy spectra during September 10, 2017, (GLE72 event) are evaluated using the results from satellite measurements, balloon observations, and neutron monitor records.

Variations in the solar-neutrino counting rates have been searched for through joint analysis of the independent data from Cl-Ar (Davis’ experiment) and Ga-Ge (SAGE experiment) detectors. The measurement data from these two detectors cover the period from 1970 to 2005. Quasi-two-year variations in the counting rates of the Cl-Ar and Ga-Ge detectors and a correlation between their sessions with a high counting rate and intense cosmic-ray flares on the Sun have been found.