Vol 35, No 5 (2019)

Abstract—The propagation of solar cosmic rays (SCR) in the interplanetary medium is considered on the basis of the Fokker–Planck kinetic equation. It is known that the SCR distribution function averaged over a solar proton event contains valuable data on the scattering process for energetic charged particles by interplanetary magnetic fields. A steady-state solution for the kinetic equation in the small-angle approximation is obtained, and the dependence of the angular distribution function of cosmic rays on the distance to the particle source is examined. This solution is applicable if the distance to the particle source is short compared to the mean free path of cosmic rays and if particles are moving primarily in the radial direction. The angular distribution of particles at large (compared to the mean free path of cosmic rays) distances to the particle source is also analyzed. An analytical expression for the distribution function of cosmic rays in the form of a sum of an isotropic component and a small anisotropic one is derived. It is demonstrated that the angular distribution of cosmic rays depends to a considerable extent on the anisotropy of their scattering. The scattering characteristics of energetic charged particles by fluctuations of interplanetary magnetic fields are estimated based on observational data for several SCR flares.

Abstract—Comprehensive modeling studies of the processes induced in all geospheres by the passage and explosion of the meteoroid near the city of Lipetsk (Russia) on June 21, 2018, have been performed. Thermodynamic and plasma effects and the effects of the plume and turbulence accompanying the passage of the Lipetsk meteoroid have been estimated. It has been shown that the passage of the celestial body led to the formation of a gas–dust plume. The heated trail of the meteoroid cooled for several hours. Four stages of meteoroid-trail cooling are considered in detail. The first of these persisted for approximately 0.01 s, and the temperature of the trail decreased by a factor of two due to emissions. During the second stage (~1 s), the trail cooled due to emissions and expansion, and its temperature decreased by 15%. In the course of the third stage, which took approximately 3 s, the products of the explosion and the heated gas (thermal) with an acceleration of 100–200 m/s², attained an ascent rate of 200 m/s, and the temperature decreased by 10%. The fourth stage persisted for 100 s, during which the thermal absorbed the cool air at an intensive rate, gradually cooled off, and decelerated. The maximum altitude of rise of the thermal reached 15–20 km. The products of the explosion (dust particles and aerosols) contained in the thermal further participated in the following three processes: a slow precipitation to the surface of the Earth, turbulent mixing with the ambient air, and transport by the predominant winds around the globe. The effect of turbulence in the trail has been shown to be well pronounced, while the effect of magnetic turbulence has been weakly displayed. The following basic parameters of the plasma in the trail have been estimated: the altitude dependences of the electron densities per unit length and per unit volume, their relaxation times, the particle collision frequencies, the plasma conductivities, and the electron temperature relaxation time. At the initial time point, the linear and volume electron densities in the trail have been shown to be equal to approximately (2–40) × 10²³ m^–1 and (1–4) × 10²¹ m^–3, respectively, and the plasma conductivity to be equal to ~10³ Ohm^–1 m^–1. The role of the dusty plasma component is discussed.

Abstract—From 2D-spectral observation data of a quiet region of the solar disk center in the Fe I λ 557.609 nm line, 3D hydrodynamic models of photospheric jets are built by solving the inverse radiative transfer problem. The obtained models describe thermodynamic parameters and the complete velocity field (vertical and horizontal). It is shown that the photospheric jets under consideration arise from the interaction of the surrounding environment with the field of the magnetic tube. The jets are located in a region of a unipolar magnetized downflow at the impact point of two horizontal flows, and they tend to occur at the edge of magnetic tubes. The observed gas velocities are subsonic in downflows of the jets. Energy release in the photospheric jets is predominantly localized in the middle photosphere layers, where the excess pressure is maximal. Compared with the surrounding media, mass density in the jets is significantly increased in the upper layers and slightly decreased in the lower layers of the photosphere.