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.

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.

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.

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.

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.

A comparative analysis has been carried out of the parameters of energetic electrons in the tail of the Earth's magnetosphere that belong to three sources, i.e., electrons of solar origin, electrons generated in the magnetosphere of Jupiter, and electrons in the Earth's magnetosphere. The differences in the time profiles of fluxes and energy spectra of the three electron sources, their relation to fluxes outside the magnetosphere, and periods of the occurrence of electron fluxes of each type are considered.

The energy spectra and relative abundances of 3He, 4He, C, O, and Fe ions with energies of ~0.04–2 MeV/nucleon are studied using data from the ULEIS instrument on board the ACE spacecraft obtained during quiescent periods in 2006–2012. During the unique, prolonged minimum between cycles 23 and 24, 35 quiescent periods were distnguished, during which solar-wind flows from near-equatorial coronal holes (CHs) were detected. It is shown that the C/O and Fe/O ratios for suprathermal ions correspond to the relative abundances of the corresponding thermal ions in the fast and slow (Maxwellian) solar wind (SWICS/ACE), while the 4He/O ratio exceeds the corresponding ratio in the solar wind by a factor of two. The intensities of the 3He, 4He, C, O, and Fe suprathermal ions in outflows from CHs grow with the speed of the solar wind. This indicates that, in periods ofminimumsolar activity, suprathermal ions from CHs represent a high-temperature “tail” of the solar wind. An additional flux of suprathermal helium ions may also be contributed by other external sources.

Показано, что, несмотря на низкую солнечную активность на фазе роста и максимума цикла 24, число солнечных протонных событий (СПС) с энергией протонов Е > 10 МэВ и Е > 100 МэВ в этом цикле мало отличается от числа таких же событий в предшествующих циклах 21–23. При этом наблюдается дефицит наиболее мощных событий типа GLE, которые характеризуются высокими значениями потока протонов с Е > 100 МэВ. Отношение числа СПС с Е > 10 МэВ и Е > 100 МэВ к числу солнечных пятен в цикле 24 выросло вдвое по сравнению с циклами 21–23, а относительное число GLE вдвое уменьшилось. Характеристики вспышек и выбросов корональной массы, ассоциированных с протонными событиями с Е > 100 МэВ, в цикле 24 практически не отличаются от аналогичных параметров в цикле 23.

The solar proton singularities in cycles 20–23 were compared. For such a comparison, it is of special importance to present information about solar proton events (SPEs) uniformly. The Katalog working group, including representatives of different institutions, created SPE catalogs for 1970–2010. These catalogs include solar events with E ≥ 10 MeV proton fluxes exceeding 1 cm−2 s−1 sr−1 near the Earth. The various conditions that accompany SPEs result in a considerable scatter of the flux parameters and energy spectra and in a difference in time profiles. Regularities in the distribution of these parameters during four solar activity cycles can be specifically revealed only based on a statistical approach that is used in this work. In this case a comparison can be successful only when the analyzed data series are homogeneous. Solar activity singularities during the entire period of SPE measurements (from cycle 19 to the end of cycle 23) are described. The methods for adjusting solar events in particles that are registered near the Earth to solar sources are of special importance. These statistical data suggest that the number of SPEs in the cycles and the event distribution within a solar cycle may indicate that the SPE generation character is different in cycles 20–21 and 22–23.

Particle fluxes in the Earth’s magnetosphere at great distances from the Earth (20 Re and more) are measured very rarely, though their behaviour is important for understanding the mechanisms of solar particle penetration into magnetosphere. The orbit and equipment of the IMP-8 Earth satellite help to overcome this deficiency to some extent. An analysis of electron fluxes with MeV energies in different parts of the IMP-8’s orbit is performed, both inside and outside the magnetosphere, and upon entering and leaving it. Bursts of electron fluxes are observed in the magnetotail during quiet periods of solar activity. These bursts could be caused by acceleration in the magnetosphere, the penetration of solar and Galactic particles, or electrons from the Jovian magnetosphere.