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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.

The paper reports the results of simulation of cosmic ray proton transport through Earth’s atmosphere. The main objective of this work is to obtain characteristics of secondary particle fluxes at different altitudes 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 galactic cosmic rays and solar cosmic rays. The computational results are tabulated for the altitude range from 0 km to 11 km above sea level; the upper range value corresponds to the flight altitude of civilian airliners. These results are shown to agree well with the results obtained by other research teams.

The mechanisms of the production of vibrationally excited NO and N2 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 N2(X1Σg+,v′ > 0) during high‐energetic proton precipitation has shown different principal mechanisms in the N2(X1Σg+,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 N2(A3Σu+)+N2 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(X2Π,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. Plain Language Summary: The Ground Level Enhancement on 20 January 2005 is the strongest event of precipitation of energetic protons in the Earth's atmosphere. We study molecular processes at the altitudes of the middle atmosphere during the precipitation. Special attention is paid to a modeling of vibrational kinetics of molecular nitrogen N2 and nitric oxide NO. The influence of electronically excited states of N2 and NO molecules on the vibrational kinetics is considered. The intensities of NO 5.3 and 2.7 μm infrared emissions are calculated. 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. Key Points: Vibrational kinetics of NO and N2 in the middle atmosphere during high‐energetic proton precipitation is consideredIntramolecular and intermolecular electron energy transfers are taken into account in calculations of vibrational populations of moleculesIt is shown that there is a dependence of calculated vibrational populations on atmospheric altitude [ABSTRACT FROM AUTHOR]