Original experiments were carried out using a gamma-ray spectrometer installed at the cosmic ray station in Apatity. The spectrometer monitors the differential spectrum of gamma radiation coming from the atmosphere in the energy range of 0.1—4 MeV. Based on the results of these experiments, a final and unambiguous conclusion was made: the effect of an increase in gamma radiation during precipitation recorded at many stations of cosmic rays is not associated with the presence of radionuclides in precipitation or additional release of radionuclides from the soil. The effect is not related to radionuclides at all. The experiments confirm the hypothesis of the influence of meteorological processes on the propagation and interaction of secondary cosmic rays in the Earth’s atmosphere.

New experiments are performed using a gamma ray spectrometer installed at the cosmic ray station in Apatity. The spectrometer monitors the differential spectrum of gamma radiation coming from the atmosphere in the 0.1–4 MeV range of energies. Analysis of the gamma radiation spectra in dozens of increases shows that the effect of growing gamma radiation during precipitation is not related to the presence of radionuclides, or the additional release of radionuclides from the soil. The characteristics of the gamma ray spectra indicate meteorological processes in the atmosphere as the primary cause of the increase effect.

The article considers the production kinetics of vibrationally excited NO(X2Π, v > 0) molecules at heights of Earth’s middle atmosphere during the precipitation of high-energy protons. The intensity profiles of the luminescence of the infrared bands of nitric oxide at 5.3 and 2.7 μm were calculated for precipitation of high-energy protons into Earth’s atmosphere during the events GLE65, GLE67, GLE69, and GLE70 of the 23rd solar cycle. Calculations have shown that the highest integral luminescence intensity values of the 5.3 and 2.7 μm bands were obtained for GLE69: 5.7 and 0.18 kR (kilorayleighs), respectively. Comparison of the calculation results for the 5.3 µm band during the GLE69 event with experimental data obtained from the TIMED spacecraft on January 20, 2005, showed that the calculation results were overestimated by a factor of 2.

The work is devoted to the study of a little-studied phenomenon: an increase in X-ray and gamma radiation coming from the atmosphere during precipitation. In this work, attention is focused on the analysis of long-term increase events, which occur rarely and differ from typical increase events in slow growth and the presence of many maxima. A differential spectrum meter for electromagnetic radiation in the range of 0.1–4 MeV is used. An analysis of the spectra measured in long-term increase events showed that the characteristics of the spectra do not differ from the same characteristics in ordinary increases. It is concluded that long-term events do not differ from ordinary ones and are due to the same reasons.

A system has been developed that makes it possible to evaluate the equivalent radiation dose at the altitudes of airliners in real time. A brief description of the calculation methodology is presented, a link is given to an information resource that provides data in the public domain. The result is shown for a typical spectrum of cosmic ray protons obtained from a satellite.

The mechanisms of the production of vibrationally excited NO and N 2 molecules at the altitudes of the middle atmosphere of the Earth during high‐energetic proton precipitation on 20 January 2005 are considered. The study of vibrational populations N 2 (X 1 Σ g + , v ′ > 0) during high‐energetic proton precipitation has shown different principal mechanisms in the N 2 (X 1 Σ g + , v ′ > 0) excitation. First, the excitation by secondary electrons is principal for vibrational levels v ′ = 1−10. Second, it is obtained that intramolecular electron energy transfer process in N 2 (A 3 Σ u + )+N 2 collisions dominates in vibrational excitation of high vibrational levels v ′ = 20−30. It is shown that the chemical reaction of metastable atomic nitrogen with molecular oxygen is the main production mechanism of vibrationally excited NO(X 2 Π, v > 0) and of the radiation of 5.3 and 2.7 μm infrared emissions at these altitudes. The calculated intensities of the 5.3 μm emission are compared with experimental data from SABER instrument on TIMED spacecraft received at the time of the proton precipitation. The role of VV′‐processes in the radiation of 5.3 μm infrared emission is discussed.

The first results of the operation of a pair of muon telescopes installed at the Apatity and Barentsburg stations (Svalbard) in addition to the existing neutron monitors are presented. A technique for separating small variations against the background of stronger variations caused by solar activity is proposed. With its help, a small anisotropy of cosmic rays between the directions of reception of muon telescopes was revealed. It is still difficult to judge the reasons for such anisotropy, since the period of solar activity is 11 years, and observations were made for just over a year

We report the measurement results of differential spectra of electromagnetic radiation in the range 0.1–4 MeV, which occurs in the atmosphere as a component of secondary cosmic rays. Spectral monitoring was performed using a spectrometer based on the Nai (TL) crystal in 2022–2023. The main purpose of the measurements was to determine spectral characteristics of the electromagnetic radiation during increase events, when the electromagnetic radiation flux from the atmosphere rises by tens of percent with respect to the background level. From a thorough analysis of the spectra of many dozens of events, we have drawn a conclusion that although the lines of natural radionuclides are present on the spectra and contribute their share, their total contribution to the increase events is ~0.1 of the total energy supplied during an increase. We unambiguously conclude that the effect of increasing electromagnetic radiation during precipitation is not due to the presence of radionuclides in precipitation.

Lebedev Physical Institute, Russian Academy of Sciences, 119991 Moscow, Russia Polar Geophysical Institute, Russian Academy of Sciences, 184209 Apatity, Russia Centre for Space Research, North-West University, 2520 Potchefstroom, South Africa School of Physical and Chemical Sciences, North-West University, 2745 Mmabatho, South Africa Institute for Experimental and Applied Physics, CA University in Kiel, 24118 Kiel, Germany E-mail: kalinin273@sci.lebedev.ru, gvozdevsky@pgia.ru, mkrainev46@mail.ru,

The conditions in the heliosphere are considered during the minimum phase of the sunspot cycle when the intensity of galactic cosmic rays (GCRs) attains its maximum at the Earth. These times of maximum GCR intensity are determined for the last five sunspot minima, including the present one. From the quantitative correlation between the heliospheric factors important to the modulation of GCRs in the heliosphere and the index of high-latitude photospheric magnetic field (all determined corresponding to times of GCR intensity maxima) the conclusion is made that the poloidal magnetic field of the Sun is one of the main governing factors for these heliospheric characteristics. Following this up, the dependence of proton spectra near the Earth on the index as mentioned above for the last five sunspot minima, 21/22 to 24/25, is calculated, also taking into account the strength of the heliospheric magnetic field and the tilt of the heliospheric current sheet, the solar wind speed and the position of the termination shock as the observable factors depending on the high-latitude photospheric magnetic field. The calculations are discussed with special attention paid to the comparison of spectra for the current and previous sunspot minima. The conclusion is made on the general dependence of GCR spectra on the poloidal magnetic field of the Sun.

Results are presented from analyzing the GLE73 event in terms of solar cosmic rays. The GLE73 event raised the count by 2–6% at polar stations of the World Neutron Monitor Network. A direct solution to the inverse problem is found, along with and the energy spectra of solar cosmic rays at the boundary of the magnetosphere are obtained and the pitch angle distribution of the flux.

The paper reports the results of simulation of cosmic ray proton transport through Earth's atmos-phere. The main objective of this work is to obtain char-acteristics of secondary particle fluxes at different alti-tudes and to convert them to equivalent dose values. The technique for the conversion is based on numerical simulation of interaction between the particles and an anthropomorphic phantom. The paper examines two cases, using a model source of primary proton spectra as input parameters, which correspond to both purely ga-lactic cosmic rays and solar cosmic rays. The computa-tional results are tabulated for the altitude range from 0 km to 11 km above sea level; the upper range value cor-responds to the flight altitude of civilian airliners. These results are shown to agree well with the results obtained by other research teams.

Results are presented from the numerical modeling of two independent GLE events that occur at different times and have different energy characteristics of protons in primary particles. The resulting dependences are analyzed with allowance for features caused by characteristics of each spectrum.

The Irkutsk 3 cosmic ray station (Mount Khulugaysha, Eastern Sayans, 3000 m) receives an additional neutron monitor section equipped with a high-speed data acquisition system developed at the Polar Geophysical Institute. It is the first time a high-speed data acquisition system is installed at a high-altitude neutron monitor. Characteristics of multiplicity events at lowland and high-altitude stations are compared to reveal substantial differences between multiplicity events.

Results are presented from modeling two different conditions for parameterizing the geometry of Earth’s atmosphere and the spectrum of primary cosmic rays. In the first, the input data correspond to solar cosmic rays and calculations are made for all geographic latitudes and longitudes. The second is devoted to estimating the contribution from the nuclei of galactic cosmic rays while considering only a local region of the atmosphere.

Energetic particle precipitation induces ionization of the atmosphere which initiates a chain of reaction cycles affecting atmospheric composition and dynamics potentially down to surface weather systems. Ionization rates are retrieved based on yield functions or pre-calculated monoenergetic electron flux and energy spectra of precipitated energetic particles. Usually, information about energy spectra is obtained from satellites, balloons, and various ground-based observations. In all cases, some assumptions about spectral distribution for the entire energy range have to be made. As ionization rates are widely used in chemistry-climate models to estimate the atmospheric response to particle forcing, evaluation of the energy spectra is a key task in the solar-terrestrial studies. In this paper, it is shown that possible uncertainties of the ionization rates retrieval based on different spectral functions can lead to large disagreements in the ionization rates, with implications for the modelled response of atmospheric composition and dynamics to electron precipitation.

The paper summarizes the properties of precipitation of magnetospheric electrons with energy above several hundred keV recorded by observing X‐ray bremsstrahlung in the polar stratosphere above the Murmansk region, Russia, in 1961–2019. Precipitation occurrence rate demonstrates a clear dependence on the solar activity with a maximum at the decay phase of the 11‐year solar cycle, similarly to the variability in occurrences of the high‐speed solar wind streams (HSSWS). The energetic electron precipitation (EEP) event series is often initiated by a moderate geomagnetic storm caused by a HSSWS and continues during geomagnetic storm recovery. EEP demonstrates the seasonal rate variation with the maxima in occurrence rate around the spring and the autumn solstices and correlates with fluences of relativistic electrons in the outer radiation belt. For 59 years, 589 events of precipitation were observed. Analysis of the long‐term time series revealed a growing trend in the rate of precipitation occurrence, especially in the 1990s to 2000s that is not properly explained yet.

The cosmic ray laboratory of the Polar Geophysical Institute has created a simple and compact telescope with a modular design that is designed to detect ionizing particles in the energy range from 1 MeV to 100 GeV. The telescope consists of two scintillator plates separated by a layer of lead that are located one above the other. The electronic circuit creates a channel for counting the upper detector and a channel of coincidences with the lower one. The area of each detector is 0.25 m2; the average count rate of the upper detector is 3000 pulses/min.

Soft gamma radiation that appears in the atmosphere as part of secondary cosmic rays has so far been studied very poorly. Observations with a gamma-ray detector designed at the Polar Geophysical Institute began in 2010 at cosmic-ray stations in Apatity and Barentsburg (in the Spitsbergen Archipelago). Observations are now being made at six stations. Two types of variation, annual and daily, are reliably observed in the data obtained with the detectors. The annual variation is associated with the formation of a stable snow cover during the cold season. The daily variation has a specific feature: the positions of its maximum and minimum differ from the analogous quantities in neutron monitors and muon detectors.

The geomagnetic cutoff rigidities for vertical and inclined detectors of the World Network neutron monitors and muon telescopes were obtained with an annual resolution for the period 1950 2015 and for the forecast time up to 2050 by the method of trajectory calculations on the basis of the IGRF model. The results of the calculations indicate the manifestation of two World anomalies of the time dependence of the rigidity of geomagnetic cutoff and an irregular course for the north-western and south-eastern directions for detectors in the northern and southern hemispheres.