Problems associated with observations and interpretation of the physical mechanisms underlying the generation of hard electromagnetic radiation from lightning discharges are considered. A review of ...modern problems of understanding the nature of atmospheric flashes of gamma radiation from the Earth’s atmosphere is given. The results of orbital observations, in particular, on the
Vernov
satellite, are analyzed. The possibilities of orbital observations of atmospheric gamma-ray flashes on CubeSat spacecraft are discussed, and a description of the recording equipment is given. The technique of a laboratory experiment with long sparks, which simulates electrical discharges in thunderclouds, is considered.
Computer simulation of the dislocation ensemble behavior in the elastic field of disclination dipole and the external stress during deformation is performed. It is shown that disclination dipole ...disturbs the laminar flow of dislocations. This leads to the appearance of sub-boundary dislocations of opposite signs, which effectively screens the disclination elastic field. Formation of junction disclinations and terminated dislocation boundaries during plastic deformation is investigated in the model bi-crystal and tri-crystal.
The change in the energy of a crystal induced by subgrain boundary formation during plastic deformation is studied by computer simulation. The crystal is shown to react to the changes caused by the ...appearance of plastic misfits: it changes its defect structure to minimize an increase in its elastic energy.
The conditions of possible microcrack nucleation and stability in the elastic field of disclinations screened by a free surface, disclinations of the opposite sense, or a distributed ensemble of ...moving dislocations are considered. The plastic deformation screening the elastic field of a disclination is shown to effectively stabilize microcrack growth at a sufficiently large grain size.
Conditions of microcrack stability in elastic wedge-disclination field screened by a distributed dislocation ensemble have been considered. The value of threshold disclination strength, above which a ...microcrack may exist, is determined. It is shown that the plastic deformation screening the elastic disclination field stabilizes the microcrack growth.
A kinetic theory of correlation interaction in an ensemble of edge dislocations is developed taking into account the effects of the fluctuation dynamics of dislocations. Equations of evolution of a ...dislocation ensemble are derived including the correlation interaction between dislocations. A criterion of instability of a uniform dislocation distribution is established. It is shown that the nucleation of spatially nonhomogeneous dislocation structures due to correlation instability is mainly determined by the specific features of the elastic interaction between dislocations and depends only slightly on the mechanism of dislocation kinetics. The theory is applied to calculating the dispersion of an internal stress field.
The self-consisted dynamics of a dislocation ensemble in the elastic field of the disclination located at the interface of two half-spaces has been considered for two cases, namely, for half-spaces ...with different densities of mobile dislocations and for a bicrystal where dislocations are absent in one half-space. The elastic energy
W
of the disclination screened by the dislocation ensemble has been calculated for the rectangular zone centered relative to the disclination. It has been shown that
W
increases as ∼
(
R
is the transverse size of the zone in the plastically deformed half-space).
The self-consistent dynamics of a dislocation ensemble in an elastic field of a planar mesodefect has been considered within the kinetic approach. The effective Airy stress function for a planar ...mesodefect, which takes into account the screening effect of a system of distributed dislocation charges, has been obtained. Coordinate dependences of the stress tensor components and the dislocation charge density for the considered screened system have been found. Its elastic energy and misorientation of the regions adjacent to the planar mesodefect have been calculated.
