卷 45, 编号 3 (2019)

Continuous-spectrum equations for low-frequency ideal magnetohydrodynamic perturbations in toroidally rotating plasmas with anisotropic pressure in axisymmetric tokamaks are derived in the framework of the Chew–Goldberger–Low model. In the rotating coordinate system, these equations describe the toroidal coupling of Alfvén and slow magnetosonic modes due to the curvature of magnetic field lines, the pressure anisotropy, and the centrifugal and Coriolis effects. The derived general equations are applied to study the spectra of both the zonal flows and the general electromagnetic modes in low-pressure large-aspect-ratio tokamaks. The condition for the instability of zonal flows due to plasma stratification over the poloidal angle on a magnetic surface is obtained. It is shown that a similar instability takes place for the general modes localized in the vicinities of rational magnetic surfaces. Stabilization of this instability by the Alfvén effect for the modes localized far from rational surfaces is shown.

The specific power deposited in plasma under on-axis electron-cyclotron resonance heating (ECRH) is characterized by strong peaking, resulting in large-amplitude sawtooth oscillations. To analyze the global properties of plasma, instantaneous experimental profiles of the electron temperature should be averaged over time and space. In the present work, a modified canonical profile transport model for predictive calculation of such averaged profiles is proposed. As an example, the model is used to determine the parameters of plasma with ECRH in the T-15MD tokamak currently under construction.

The phenomena occurring under head-on collision of ion-acoustic solitary waves in collisionless plasma consisting of positive and negative ions and electrons obeying the Boltzmann distribution are considered. Using particle-in-cell simulations, it is shown that large-amplitude compressive ion-acoustic solitary waves do not preserve their identity after the collision. Their amplitudes decrease and their shapes change. It is shown that the collision is accompanied by the generation of fast positive ions the velocity of which can exceed more than threefold the speed of sound. In addition, the collision is accompanied by the trapping of negative ions by the field of ion-acoustic solitary waves formed after the collision.

Results are presented from analytical and numerical studies of the effect of a dc magnetic field on the spectral characteristics of thermal motion of charged particles in an isotropic electrostatic trap. An analytic expression for the spectral density of the shifts of the center of mass of the systems under study is obtained. The analytic expression is verified by numerically simulating ensembles with different numbers of particles interacting via the Coulomb potential in a wide range of parameters.

UV radiation of high-voltage pulsed multispark surface discharge in atmospheric-pressure air in the spectral range of 200–380 nm was investigated. The discharge was a sequence of microplasma objects with a specific energy deposition of ~1 kJ/cm³ and electron density of 10¹⁷ cm^–3. Copper and stainless steel were used as the electrode materials. It is found that lines of atoms and ions of the electrode material dominate in the discharge UV spectrum. The UV radiation intensity was measured using the actinometry technique. The UV radiation efficiency relative to the energy deposited in the discharge is found to be ~1%.

Details of the process of lightning formation and orientation of the downward leader required to solve applied problems in the field of lightning protection are considered. It is shown that it is necessary to take into account the mechanism of the bipolar leader formation in the thundercloud electric field, according to which the thunderstorm cell cannot be regarded as a conducting charged electrode, the potential carried by the downward leader channel is determined by the start point and path of the lightning, and the effect of the thunderstorm cell charge reveals itself to a much less degree. An algorithm is proposed for calculating the orientation height, charge per unit channel length, and attraction radius of lightning from the value of the return stroke current. It is stated that lightning current measurements currently used at tall structures cannot serve as a basis to estimate the frequency of dangerous lightning strikes to structures of ordinary height. A scheme of the field research of lightning is proposed that allows the required statistics of lightning currents to be accumulated for a foreseeable time period at admissible material costs. The need to study the mechanism of the competing development of counter discharges from ground-based electrodes is proven, and the relevant technique is offered.

The propagation of the front of a single surface dielectric barrier microdischarge is studied using an analytical model based on the charge balance equation. The model allows one to find analytical dependences of the discharge propagation velocity and the length of the discharge zone on the parameters of the dielectric barrier and applied voltage pulse. To solve the problem, the results of numerical simulations of the distributions of the electric field, potential, and electron density along the discharge channel are used. The results obtained with the help of the proposed model agree qualitatively with available experimental data.

The measurement technique and results are presented from studies of the spectral composition of X-ray emission from different regions of micropinch discharge plasma in a low-inductive vacuum spark device. X-ray spectra are measured in the photon energy range of 1–30 keV for the radiation emerging from the plasma spot, near-anode plasma, and anode regions of the micropinch discharge plasma. It is experimentally established that, in the energy range under study, the intensity of X-ray emission from the plasma spot exceeds that from the near-anode and anode regions.

The boundary (line) of the transition from homogenous dust structures to hollow dust structures in the coordinates gas pressure–discharge current in a glow discharge in neon was found experimentally. The experiments were carried out with spherical particles 2.55 and 4.14 μm in diameter. The transition was simulated using the diffusion–drift model of the positive column of a glow discharge in neon with allowance for the radial temperature gradient. Simulations of the experimental data have shown that the thermophoretic force acting on the microparticles in the dust structure depends on the discharge parameters and the dimensions of the microparticles and the dust structure. The results of this work can be used in dusty plasma technologies.