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The possibility of the existence of radiation belts near a planet possessing an intrinsic magnetic field and located in a stellar plasma flow is considered using Mercury as an example. An analysis is performed both using Stormer’s theory of charged particle motion, in which not the specific trajectories of individual particles, but the regions of allowed motion in an axisymmetric field are considered, and by analyzing the trajectories. The existence of trapped radiation near Mercury is shown to be possible, and the criteria for the formation of a stable population of trapped particles are formulated.

The paper considers the classification of solar wind streams in magnetohydrodynamic parameters (MHD-types); combinations of proton speed, density, temperature, and magnetic field strength, in addition to the classical solar wind separation into high-speed streams from coronal holes, transient streams of coronal mass ejections, and the slow solar wind from the streamer belt. Two classifications of solar wind properties were compared for the events in August 2010 and May 2011, when one could observe the interaction of two coronal mass ejections and a coronal mass ejection with a high-speed solar wind stream from the coronal hole, respectively. It is shown that the classical description of a large-scale structure of wind streams (the ion wind composition especially) in scales of hours and days allows one to determine the type and source of streams, whereas the MHD-parameters allow one to more accurately describe the small-scale structure (in minutes), especially in the cases of several streams interaction in the heliosphere. The detailed study of a small-scale structure of stream interaction regions provides the information required for developing MHD-models describing the processes of propagation and interaction of streams in the heliosphere and for predicting their geoefficiency.

At the present time, there is no generally accepted classification of the solar wind flows. There are various approaches to this problem depending on the goal of the study. In our paper, we propose the binary classification of the solar wind types by the main hydrodynamic parameters (velocity, temperature, and density) based on the statistical analysis of the solar wind. The analysis of the OMNIWeb one-minute data is performed for the period from 1996 to 2017, which encompasses solar cycle 23 and current solar cycle 24. Eight types of the solar wind are distinguished: fast-hot-dense, fast-hot-rarefied, fast-cold-dense, fast-cold-rarefied, slow-hot-dense, slow-hot-rarefied, slow-cold-dense, slow-cold-rarefied. These types occur with different frequency and are the consequences of different manifestations of solar activity. Of particular interest are the solar wind flows, the parameters of which deviate from the averages most significantly.

A binary classification of solar wind types is given according to three main hydrodynamic parameters—the proton speed, the proton temperature, and the proton density. Boundaries between the fast–hot–dense, fast–hot–rarefied, fast–cold–dense, fast–cold–rarefied, slow–hot–dense, slow–hot–rarefied, slow–cold–dense, and slow–cold–rarefied solar wind types are specified in the space of these variables. These types arise at different frequencies and originate from different sorts of solar activity. An analysis of 1-minute data from the OMNIWeb database is performed over the period from January 1, 2016, to September 30, 2017. In some cases, this classification scheme, which is quite simple and clear, allows one to identify the sources of the solar wind (coronal holes and coronal mass ejections), as well as to reveal long-term trends. The proposed scheme is compared with the methods used earlier in the literature to classify solar wind types.

Based on numerical and analytical approaches, a comprehensive physical and mathematical model determining the motion and destruction of natural cosmic bodies in the Earth atmosphere is created. Multilevel interrelated problems are considered, including simulation of the aeroballistics of meteoroids and their fragments taking into account their thermal and mechanical destruction; computation of airflow around a set of bodies (the meteorite fragments); and analysis of the problem of multiple “explosions” in atmosphere, which is inherent in meteoroids moving in the atmosphere after their fragmentation. The aim of the study is to resolve an important aspect of the asteroid and comet threat—the interaction of meteoroids with the atmosphere.

In the context of studying the problem of simulation of magnetic fields on the Sun, the structure of the field in the vicinity of two circular current loops with different mutual arrangement in space is considered. When the symmetry in the arrangement is sufficient, a system of magnetic surfaces created by the closed field lines arises. With a reduction in symmetry, isolated closed lines may exist. For the case of two identical current loops coupled perpendicularly, it is shown that the subsystems of these lines may be ordered in space in a complex manner. At large distances, a system of loops is equivalent to a dipole with a high degree of accuracy, while an approximate winding of the lines on the deformed toroids, encircling each of the loops, occurs at small distances. At intermediate distances, there are regions of both ordered and chaotic behavior of field lines. Results were obtained with the use of the numerical simulation method.

General principles of describing secondand higher-order null points of a potential magnetic field are formulated. The potential near a second-order null of the general form can be specified by a linear combination of four basic functions, the list of which is presented. Near secondand higher-order null points, field line equations often cannot be integrated analytically; however, in some cases, it is possible to present a qualitative description of the geometry of null vicinities with consideration of the behavior of field lines near rays outgoing from null, at which the field is radial or equals zero.

The development of geomagnetic storms is mainly controlled by external heliospheric factors, which in turn depend on the conditions on the Sun. Magnetospheric disturbances can be isolated, repeated, multiple, or turbulent, depending on these conditions. Most geomagnetic storms develop complexly and are characterized by the existence of one or several side extrema before or after the main one. This is mainly related to the superposition of individual disturbances that follow immediately one after another from the Sun into the heliosphere or to the internal structure and dynamics of disturbances in the corona. The geomagnetic storms from the APEV extensive database for cycle 23 of solar activity, which were combined into 227 events, were analyzed in order to reveal the statistics based on single and multiple magnetospheric disturbances. The results are presented as histograms, graphs, tables, and empirical formulas for the total number of intensifications in all events and depending on different geomagnetic storm development phases, amplitude, and duration.

On the basis of experimental results from the Ulysses spacecraft, a model is proposed for calculating the magnetic field in the corona and the heliosphere in the potential approximation, which is a modification of the potential-field source-surface model. In addition to the photospheric surface and the source surface, a new demarcated spherical surface (leveling surface) is introduced in this model. The magnitude of the radial component of the magnetic field on this surface is assumed to be constant, and its sign abruptly changes from one hemisphere to another. General analytical formulas are given to calculate the potential and field for this model. Calculations are described in detail using the dipole and quadrupole harmonics as examples. Expressions are obtained for the surface currents. The results of visualization of the magnetic field for an axial dipole are discussed.