Experimental data on solar activity (sunspot number, induction of solar polar magnetic field Bp, and others), characteristics of interplanetary space, and cosmic ray fluxes testify that the Sun has entered a deep minimum of its activity similar to the Dalton minimum. An almost functional relationship was found between maximum values of Bpmax observed in the solar activity minimum of the 11-year cycle and the next sunspot maximum. Based on this relationship, a simple method of forecasting maximum number of sunspots Rzmax and time course Rz(t) was developed. A forecast of the 25th solar cycle is given.

The phases of quasi-biennial variations (QBVs) in cosmic-ray fluxes and solar-activity and interplanetary-medium parameters are investigated. A spectral analysis of QBVs of listed data was carried out. For the data used, the spectral components with a maximum amplitude (the sinusoidal component with a period of about 1.7 years (about 20.5 months)) are identified. A comparison of phases of QBVs with the phases of these sinusoids in those time intervals, where the QBVs were reliably identified unambiguously, is performed. It is shown that, according to all data, the phases of quasi-biennial variations persisted for many decades with minor deviations. This testifies to the longitudinal stability of the regions on the Sun, which are responsible for a quasi-biennial variation.

This study uses the evolution of a parameter introduced by the author that characterizes the relative position of planets: the daily average difference of the heliocentric longitudes for a pair of planets. Venus, Earth, and Jupiter are considered in pairs based on the minimum values of this parameter. We compiled an index (JEV) to describe the 11-year cycle of solar activity based on the minimum deviations of the planets from the line passing through them and the Sun when the planets are located on one side of the Sun (planets are in conjunction), as well as when the planets are located on opposite sides of the Sun and on the same line with it. In addition, the average differences were calculated for four planets with Mercury. It is shown that Mercury does not fit into the 11-year linear configurations of Venus, Earth, and Jupiter and does not participate in the maximum gravitational impact on the Sun. Only Venus, Earth, and Jupiter in their linear configurations have an 11-year cycle. The JEV index is compared with solar activity and it is shown that the average 11-year periodicity in the JEV index and in solar activity over a 1000-year time interval coincide to two decimal places. This indicates a possible relationship between the JEV index and the 11-year solar activity cycle.

The quasi-biennial variations in the flux of galactic cosmic rays (GCRs) have been studied based on the data of stratospheric sensing and measurements by neutron monitors, as well as in various manifestations of solar activity and interplanetary medium parameters. It has been shown that quasi-biennial GCR variations are caused by variations with the same period in the mean magnetic field of the Sun that coincide with them over time and have been identified in the anti-phase, which respond to the sign of this field. The variations in the quasi-biennial cosmic ray are caused by quasi-biennial variations in the mean magnetic field of the Sun via the quasi-biennial variations in the interplanetary magnetic field.

Quasiperiodic variations of various manifestations of solar activity, parameters of the interplanetary medium, and the flux of galactic cosmic rays (GCRs) are studied using the data of stratospheric sounding and measurements with neutron monitors. Groups of spectral components with periods of ~2, 1.3, and ~1 year are identified in the range of periods shorter than 5 years. Particular attention is paid to quasi-2-year GCR variations that are induced by similar variations of the mean magnetic field of the Sun and are integral to the processes of solar activity.

The periodicities of cosmic rays in the stratosphere, in the neutron component, and in different parameters of solar activity and the interplanetary medium between 1965 and 2015 are studied by means of spectral analysis. The data are analyzed separately according to cycles of solar activity. A shift of spectral components is observed in the even–odd combination of solar activity cycles.

One of the most important problems facing humanity, global climate change, is discussed. The roles of cosmic ray fluxes and solar activity in this process are analyzed. Although several mechanisms explaining global climate change have been proposed, none of them are firmly grounded. At the United Nations summit in Paris at the end of 2015, it was decided that greenhouse gases are responsible for the global warming of our planet. However, the authors of this work believe the question of what causes global changes in the Earth’s climate remains open, and will obviously be solved once and for all in the next 10–15 years.

This paper presents the calculations of the resulting tidal force of Jupiter, Venus, and Earth, that act on the Sun. Considering the tidal forces as the difference of gravitational forces that act on the extreme points of the Sun’s diameter and on the center of the Sun, it is shown that there are large variations in the resulting tidal force (RTF) at the moments of linear configurations of Venus, the Earth, and Jupiter, and that the maximum variations of the RTF are in a strong agreement with the minimum values of the JEV planetary index, as introduced by the author in previous works.

Solar proton events during a period from 1956 to 2012 are considered. Fluences of protons of various energies in these events have been computed. On the basis of these extensive data the inhomogeneity of the distribution of their sources on the Sun along the Carrington longitude has been confirmed, which had been earlier revealed in our studies. Special attention is paid to the discovered interval of "passive longitudes", extensive over the longitude (90-170°) and the life time (the whole period of observations). The summarized proton fluence of the events, which sources belong to this interval of Carrington longitudes, is considerably lower, than the summarized proton fluences of the events in the other heliolongitude intervals. From the 60 most powerful solar proton events during the whole period of observations not more than 1 event has been originated from this interval of "passive longitudes".

An analysis of long-term observations of the fluxes of interplanetary protons with energies of 1–100 MeV measured at a distance of 1 AU from the Sun is performed. The results from computations of the maximum, average, and minimum values of total interplanetary proton fluences accumulated over periods ranging from 1 month to 10 years are presented. The possibilities of applying the obtained data to characterizing and predicting space weather and climate are discussed.

The current 24th solar activity cycle started in 2008 and continuing to the present is anomalous in comparison with previous cycles. Its unusual properties include a low sunspot number R z for a long time, a weak interplanetary magnetic field, a weak polar photospheric field in the Sun, and others. Beginning in 1000 to the present, five prolonged solar activity minima took place. These minima occurred in time intervals, when the distance between the center of mass of the solar system and the Sun center changed several times from maximum to minimum values for 40–70 years. Since the beginning of the new millennium, exactly such a period started and it can be assumed that we entered a new prolonged minimum which will last for several decades. In the current 24th and subsequent 2–3 solar activity cycles, annual average sunspot numbers will be low, R zmax ≤ (50–70).

The areas of energetic particle injection on the Sun from 1956 to 2013 are considered. A significant irregularity of their heliolongitude distribution have been found. A special attention is paid to the discovered region of “passive longitudes” with very law radiation effectiveness, extensive over the longitude (≈90–170◦) and the life time (the whole period of observations). Also the distribution of the sources of energetic solar protons measured in Earth’s orbit, over the longitude relative to the central meridian have been considered. The conclusion about the validity of the obtained data for estimation of the risk of solar cosmic ray arriving is made.

In this paper, using the parameter—the average difference between the heliocentric longitudes of the planets Venus, Earth and Jupiter—the strong link found 22-year and 11-year cycles of solar activity with the lowest values of the parameter. The envelope curve of the minimum values of this parameter is well described as the conjunctions of the three planets, when they are almost in a straight line from the sun, which causes the maximum of solar activity, and the conjunctions in the larger longitudinal sector (25–30 degrees), which occur much more frequently and are accompanied by different combinations of planets on the opposite side of the Sun, which also cause the maximum of solar activity. Location of these planets on opposite sides of the Sun in various combinations is very well compatible with the parameter used.

We discuss the current solar cycle (number 24), its unusual characteristics, and the forthcoming solar maximum. We predict the solar activity over the next few decades. A prolonged solar minimum is expected, and the maximum of cycle 24 is predicted to have a low number of sunspots (annual mean number of sunspots, R z ≈ 50).

The dynamic parameters of the motion of the Sun relative to the center of mass of the Solar System, viz., the distance of the center of the Sun relative to the center of mass and the angular momentum of the Sun, as well as its changes, are investigated. The frequency spectra of these parameters and of the Wolf numbers are calculated and the main spectral components are revealed. It is shown that a periodicity of 178.8 years is not predominant in the dynamic parameters of the motion of the Sun; in this frequency range a periodicity of 169 years connected with the influence of Neptune predominates. The coincidence of the periodicities in the Wolf numbers and dynamic parameters of the motion of the Sun is shown. The causes of all components of the frequency spectrum are indicated.