Том 60, № 2 (2016)

The dependences of the magnetic-field strength, variations of the magnetic field, and the multipole level on the amplitudes of the α and ω effects are considered using a two-dimensional model for a Parker dynamo in a spherical layer. Calculations have been carried out for both traditional spatial distributions of α and ω and geostrophic regimes obtained from three-dimensional modeling of thermal convection. Two-dimensional distributions of the dynamo-wave velocities in the zone where magnetic field is generated are presented. Comparisons with the solar and planetary dynamos are considered.

Known models proposed to explain the high space velocities of pulsars based on asymmetry of the transport coefficients of different sorts of neutrinos or electromagnetic radiation can be efficient only in the presence of high magnetic fields (to 10¹⁶ G) or short rotation periods for the neutron stars (of the order of 1 ms). This current study shows that the observed velocities are not correlated with either the pulsar periods or their surface magnetic fields. The initial rotation periods are estimated in a model for the magnetedipolar deceleration of their spin, aßsuming that the pulsar ages are equal to their kinematic ages. The initial period distribution is bimodal, with peaks at 5 ms and 0.5 s, and similar to the current distribution of periods. It is shown that asymmetry of the pulsar electromagnetic radiation is insufficient to give rise to additional acceleration of pulsars during their evolution after the supernova explosion that gave birth to them. The observations testify to deceleration of the motion, most likely due to the influence of the interstellar medium and interactions with nearby objects. The time scale for the exponential decrease in the magnetic field τ_D and in the angle between the rotation axis and magnetic moment τ_ß are estimated, yielding τ_β = 1.4 million years. The derived dependence of the transverse velocity of a pulsar on the angle between the line of sight and the rotation axis of the neutron star corresponds to the expected dependence for acceleration mechanisms associated with asymmetry of the radiation emitted by the two poles of the star.

The structure of the interstellar plasma in the direction of the pulsar in the Crab Nebula is studied using several sets of space-VLBI observations obtained with networks of ground telescopes and the RadioAstron space antenna at 18 and 92 cm. Six observing sessions spanning two years are analyzed. Giant pulses are used to probe the cosmic plasma, making it possible to measure the scattering parameters without averaging. More than 4000 giant pulses were detected. The interferometer responses (visibility functions) on ground and ground–space baselines are analyzed. On the ground baselines, the visibility function as a function of delay is dominated by a narrow feature at zero delay with a width of δ_τ ~ 1/B, where B is the receiver bandwidth. This is typical for compact continuum sources. On the ground–space baselines, the visibility function contains a set of features superposed on each other and distributed within a certain interval of delays, which we identify with the scattering time for the interfering rays τ. The amplitude of the visibility function on ground baselines falls with increasing baseline; the scattering disk is partially resolved at 18 cmand fully resolved at 92 cm. Estimates of the scattering angle ? give 0.5–1.3mas at 18 cm and 14.0 mas at 92 cm. The measured values of ? and τ are compared to estimate the distance from the source to the effective scattering screen, which is found at various epochs to be located at distances from 0.33 to 0.96 of the distance from the observer to the pulsar, about 2 kpc. The screen is close to the Crab Nebula at epochs of strong scattering, confirming that scattering on inhomogeneities in the plasma in the vicinity of the nebula itself dominates at these epochs.

A model describing the main processes determining the evolution of hydrocarbon dust grains of arbitrary size under astrophysical conditions corresponding to regions of ionized hydrogen (HII regions) and supernova remnants is presented. The processes considered include aromatization and photodestruction, sputtering by electrons and ions, and shattering during collisions between grains. The model can be used to calculate the size distribution of the grains and the degree of aromatization during the evolution of HII regions and supernova remnants for a specified radiation field, relative velocity between the gas and dust, etc. The contribution of various processes to the evolution of hydrocarbon dust grains for parameters typical for the interstellar medium of our Galaxy is considered. Small grains (with fewer than 50 carbon atoms) should be fully aromatized in the interstellar medium. If larger grains initially have an aliphatic structure, this is preserved to a substantial extent. Variation in the size distribution of the grains due to collisions between grains depend appreciably on the adopted initial size distribution. With an initial distribution corresponding to that of Mathis et al. (1977), the mass fraction contributed by smaller grains tends to increase with time, while, with an initial distribution corresponding to that of Jones et al. (2013), in which the fraction of small grains is initially high, there is a general decrease in the number of grains of various sizes with time.

The results of many-year uniform spectroscopic observations of the Herbig Ae/Be star IL Cep A are presented. Its Hα line has either a single or a barely resolved two-component emission profile. The Hβ emission line is clearly divided into two components with a deep central absorption. Smooth variations of the observed parameters of individual spectral lines over nine years are observed. The He I λ5876 Å line has a complex absorption profile, probably with superposed emission components. The NaI D1, D2 doublet exhibits weak changes due to variations in the circumstellar envelope. The variations observed in the stellar spectrum can be explained by either binarity or variations of the magnetic field in the stellar disk. Difficulties associated with both these possibilities are discussed.

The Doppler motions in a filament and the underlying photosphere over the several days before its eruption are analyzed. A large filament in the northern hemisphere near the central meridian observed from August 31-September 2, 2014 erupted on September 2, 2014. The filament lost the bulk of its mass as a result of its eruption, and the process of its reconstruction had begun a day later. Observations of this filament in a spectral range encompassing the Hβ λ 486.1 nm (chromospheric) and Fe I λ 485.9 nm (photospheric) lines were carried out on the Horizontal Solar Telescope of the Sayan Solar Observatory on August 31-September 2, 2014. Analysis of the Doppler motions in and beneath the filament yielded the following results. Strong rotational motions were present in the filament over a prolonged period (the entire three days of observations). The coincidence of the steady-state motions of the photosphere and filament was disrupted at the moment of destabilization of the filament by the emergence of new magnetic flux. Short-period (about five-minute) photospheric oscillationswith a train-like character arose in filament from time to time several hours before the eruption. Large segments underwent nearly vertical oscillations in the initial phase of the ascent of the filament.