The article presents the results of a comparative analysis of the solar proton event on March 30, 2022, which has an unusual time profile of solar proton fluxes, and the previous and subsequent solar proton events (March 28, 2022, and April 02, 2022). Increases in energetic proton fluxes in the interplanetary and near-Earth space are associated with successive solar X-ray flares M4.0, X1.3, and M3.9 and three halo-type coronal mass ejections. The study was based on experimental data obtained from spacecraft located in the interplanetary space (ACE, WIND, STEREO A, and DSCOVR), in a circular polar orbit at an altitude of 850 km (Meteor-M2) and in geostationary orbit (GOES-16, Electro-L2). An explanation has been proposed for the specific features of the energetic proton flux profile in the solar proton event on March 30, 2022: protons accelerated in the flare on March 30, 2022 were partially screened by an interplanetary coronal mass ejection, the source of which was the explosive processes on the Sun on March 28, 2022; late detection of maximum proton fluxes, simultaneous for particles of different energies, is due to the arrival of particle fluxes inside an interplanetary coronal mass ejection. The spatial distribution of solar protons in near-Earth orbit was similar to the distribution at the Lagrange point L1 but with a delay of 50 min.

Представлены результаты исследования потоков солнечных протонов с энергией больше 5 МэВ в околоземном космическом пространстве 13–23.III.2023. Особенностями исследуемого периода являются отсутствие наблюдаемой солнечной вспышки, с которой можно ассоциировать начало события, нехарактерный временной профиль потоков протонов, а также большая длительность существования потоков солнечных протонов в околоземном пространстве. Предпринята попытка объяснить источники наблюдаемых вариаций потоков частиц и понять, что происходило на Солнце и в окружающем Землю пространстве. Источником солнечных протонов 13.III.2023 был взрывной процесс на обратной от Земли стороне Солнца, зарегистрированный как корональный выброс массы очень большой мощности. Причиной длительного и сложного временного профиля солнечных протонов был вклад процессов ускорения частиц на Солнце и в межпланетной среде, а также модуляция потоков частиц структурами межпланетного магнитного поля. Предложен возможный сценарий, объясняющий существование повышенных потоков солнечных частиц 15–23.III.2023: формирование гелиосферной структуры – замкнутой области-­ловушки, образованной двумя межпланетными корональными выбросами массы и областями взаимодействия высокоскоростных и медленных потоков солнечного ветра. В работе использованы экспериментальные данные, полученные с космического аппарата Solar Orbiter и с космических аппаратов, расположенных вблизи точки L1 системы Земля – Солнце (ACE и DSCOVR) и на геостационарной орбите (GOES-16).

The results of studying the fluxes of solar protons with energies greater than 5 MeV in near-Earth space on March 13–23, 2023, are presented. The features of the period under study are no visible solar flare with which the beginning of the event could be associated and an untypical time profile of proton fluxes, as well as a long duration of the existence of solar proton fluxes in near-Earth space. An attempt was made to explain the sources of the observed different variations in particle fluxes and to understand what happened on the Sun and in the near-Earth space. The source of solar protons on March 13, 2023, was an explosive process on the back side of the Sun from the Earth, registered as a coronal mass ejection of very high power. The reason for the long and complex time profile of solar protons was the contribution of particle acceleration processes on the Sun and in the interplanetary medium, as well as the modulation of particle fluxes by the structures of the interplanetary magnetic field. A possible scenario has been proposed to explain the existence of increased fluxes of solar particles on March 15–23, 2023: the formation of a heliospheric structure, this being a closed trap region formed by two interplanetary coronal mass ejections and regions of interaction of high-speed and slow solar wind streams. The study uses experimental data obtained from the Solar Orbiter spacecraft and from spacecraft located near the L1 point of the Earth–Sun system (ACE and DSCOVR) and in geostationary orbit (GOES-16).

Based on the catalogs of solar proton events for the 23rd and 24th solar cycles, events were chosen that lacked a reliable source of particles but were accompanied by interplanetary and geomagnetic disturbances. As a rule, these events involve small proton fluxes that are detected near the Earth. All of the selected events occurred during the arrival of shock waves to the Earth, suggesting that they were likely caused by the arrival of energetic storm particles. It has been shown that flares accompanied by coronal mass ejections, which occurred tens of hours before the onset of the increase in particle fluxes in Earth’s orbit, could be the source of these events. The selected events exhibited several specific features. Only one of them was accompanied by a single shock front, while the others had two or three shock waves. The time profile of the events resembled a structure bounded by two shock fronts, suggesting that the shock waves likely accelerated and confined the particles within a limited region of space.

Some of the weak solar proton events in which protons with energies E ≥ 10 MeV are registered by observers on the Earth are particles accelerated by shock waves in interplanetary space. They can be associated with flares and coronal mass ejections tens of hours before an observed increase in proton fluxes that inject particles into the process of subsequent acceleration in interplanetary space.

Distinguishing features of a series of solar proton event (SPE) catalogs for the 20th–24th cycles of solar activity are described. The results of a comparative analysis of the 23rd and 24th cycles of solar activity performed according to the data of a series of SPE catalogs are presented. The opportunities provided by SPE catalogs for studying space weather factors, such as the dynamics of solar activity, the structure and state of the interplanetary medium, and the Earth’s magnetosphere are discussed.

initiates ion-molecular reactions that affect the change in the concentration of ozone, and, as a result, the temperature and circulation of air masses in the stratosphere and troposphere of the Earth.

Homogeneous series of solar cosmic-ray events for four solar-activity cycles against the background of decreased activity in cycles 23 and 24 are considered. The number of solar cosmic-ray events with energies above 10 MeV decreased insignificantly, while the number of ground-level enhancements in comparison between cycles 23 and 24 decreased by eight times. It is shown that the average contribution of flares to the generation of ground-level enhancements decreased from cycle 23 to cycle 24 by three times, and the average contribution of coronal mass ejections decreased by five times; the average contribution of flares to the generation of solar cosmic rays with energy >10 MeV decreased by 1.3 times, and the average contribution of coronal mass ejections increased by 1.4 times.

Type-II radio emission often accompanies events in solar cosmic rays and is an indicator of the propagation of a shock wave in the solar corona. Conversely, the shock wave associated with coronal mass ejections plays an important role in the acceleration of solar protons. Both of these phenomena can occur unaccompanied by solar cosmic rays, while not all solar cosmic ray events are accompanied by type-II radio emission. The statistical relationships between these phenomena are considered based on the catalogs of solar proton events for the 23rd and 24th solar-activity cycles. It is shown that the events of solar cosmic rays accompanied by type-II radio emissions are among the most powerful in terms of both particle characteristics and source characteristics.

A combination of two power laws is used to present spectra of electrons in the MeV range of energies, measured during the solar activity minimum in 2007−2008 by the Electron Proton Helium Instrument (EPHIN) on board the Solar and Heliospheric Observatory (SOHO). The power index for electrons with energies higher than 0.7 MeV is γ ≈ 1.5–1.6, testifying to their Jovian origin. For electrons with lower energies, γ ≥ 3.5. In combination with short-term bursts (lasting for 2–3 days) in the intensity of electrons and protons with energies on the order of hundreds of keV (according to data from the Electron Proton Alpha Monitor (EPAM) on board the Advanced Composition Explorer (ACE) and the Low-nergy Ion and electron (LION) instrument on board the SOHO, respectively), this value suggests that low-energy particles are accelerated in the interplanetary medium.

Solar proton events are compared using the Catalogue of Solar Proton Events of the 24th Cycle of Solar Activity and solar events with long-duration high-energy gamma radiation based on measurements at the Fermi gamma-ray telescope. High-energy γ-quanta are mainly the product of the decay of π о -mesons during the interaction of high-energy protons on the Sun. Sources of gamma-ray flares not accompanied by solar protons are located in the eastern hemisphere of the Sun, and the associated coronal ejections do not move toward the Earth. Solar protons from such sources are not recorded by the terrestrial observer.

ABSTRACT This work studies the influence of the structure of inner heliospheric magnetic field on the propagation of Jovian electrons from Jupiter to the Earth orbit. Beginning from 1974, 13-month variations of relativistic Jovian electron fluxes were recorded by spacecraft near the Earth. 22 synodic cycles are analysed. The best connection in each cycle was found within a narrow longitudinal interval with an angular divergence of the planets 230 ± 20°, when the Parker field line connecting the two planets is formed at solar wind speed 450 ± 50 km s−1. Such invariability for more than 45 yr could not be accidental. We attribute the observed phenomenon to the long-term presence of recurrent stationary structures in the solar wind generated near the Sun. This assumption is confirmed by comparing the time profiles of the solar wind speed measured over all solar rotations in the solar activity minima in 1975 and 2007–2008.

Solar proton events possess a wide variety of features that reflect the conditions of solar proton acceleration and propagation. Relevant investigations rely on statistical methods that make it possible to classify events with the aim of obtaining deeper insight into physical processes leading to the generation of solar cosmic rays. In classifying events in power, the intensity of particles with energy above 10MeV at the maximum of the event time profile or the fluence of particles throughout the event time is usually used. A new parameter, E (qm), that characterizes the proton event power and which is some kind of approximation of the maximum energy of accelerated particles is analyzed in the present study. Correlations of E (qm) with properties of x-ray flares on the Sun and with the velocity of coronal mass ejections are examined.

The results from observing Jovian electrons in the vicinity of the Earth are discussed. Variations in Jovian electron flows are observed during 14 rotations of the Sun in 2007–2008. The results are analyzed by assuming the existence of magnetic traps in the space between the Sun and Jupiter that are filled with electrons near Jupiter, and are then registered when the traps pass by the Earth. The average period of variation in the Jovian electron flow during the 14 solar rotations is 26.2 days instead of the expected synodic period of the Sun–Earth system equal to 27.3 days. An explanation for this phenomenon is proposed.

Variations in the flux of Jovian electrons near the Earth in two synodic cycles of the Earth–Jupiter system, in 1974–1975 and 2007–2008, are considered. In the 1974–1975 cycle, Jovian electrons were observed by IMP-8 during 13 successive solar rotations; electrons were observed by SOHO during 14 solar rotations during the 2007–2008 cycle. The fluxes of these electrons in each solar revolution experienced variations with a characteristic time scale of ~27 d , with the maximum flux near the middle of the rotation. The mean period of the variations does not coincide with the synodic period for the Sun–Earth system, equal to 27.3 d . The mean variation periods for the electron fluxes were 26.8 d in 1974–1975 and 26.1 d in 2007–2008. The detected variations are interpreted as reflecting variations in the structure of the solar wind speed and associated magnetic traps, the confinement time of the electrons in thesemagnetic traps, and the influence of the relative positions of the Earth and Jupiter in space.