Том 49, № 3 (2023)
SPACE PLASMA
Wave Processes in Plasma Astrophysics
Аннотация
Theoretical studies of wave processes in rotating astrophysical plasma are discussed, with a particular emphasis on new theoretical models of astrophysical plasma such as the magnetohydrodynamic shallow water approximation and anelastic approximation, together with the frequently-used Boussinesq approximation. In addition to the traditional approximation for Coriolis force, effects are discussed, which are caused by its non-traditional representation that accounts for the horizontal rotation component. Linear waves in such plasma are described in detail, and their dispersion properties are discussed. An overview of instabilities in astrophysical plasma is given, which are caused by nonlinear effects.
209-259
OSCILLATIONS AND WAVES IN PLASMA
Microwave Low-Pressure Gas Discharge Sustained by a Standing Surface Wave in the Dipolar Mode
Аннотация
The maintenance of a microwave gas discharge of a standing surface electromagnetic wave (SEW) in the dipolar mode is studied. The standing wave was formed between two flat mirrors that create an open resonator type structure on the surface wave. The measured Q factor of the open resonator is several tens. The electric field structures of a free discharge and a discharge supported by a standing surface wave field are determined. It is shown that resonance on a purely surface wave is excited in this system. With an increase in the field energy between the mirrors by 8–10 dB, the concentration of electrons increases by about 50%. The ratios of the surface wave field energies in the plasma and in the space surrounding the discharge both in the case of a free discharge and during resonance are estimated. The results of experiments and numerical simulations show that the structure of the discharge depends on the excited mode of steady-state SEWs.
260-269
On One Widely-Spread Inaccuracy and Its Elimination in the Theories of Nonlinear Electrostatic Waves in Plasma Based on the Sagdeev’s Pseudopotential Approach
Аннотация
We report on the discovery of a contradiction appearing in the solutions to the problems of profiles of the nonlinear longitudinal electrostatic waves in plasma obtained using the Sagdeev’s pseudopotential approach. The contradiction reveals itself in the average over period particle concentration and given concentration of the unperturbed plasma being unequal to each other. It is demonstrated that the reason for the appearance of this contradiction is related to the relatively widely spread inaccuracy in the formulation of such problems. It is suggested correcting the formulation of such problems and changing interpretation of solutions obtained using the approach under consideration by imposing different initial conditions: it is necessary specifying particle concentration at the points where potential φ is set equal to zero instead of concentration of the unperturbed plasma. The contradiction is resolved completely when using such initial conditions.
270-277
LOW TEMPERATURE PLASMA
On the Concept of Plasma Mass-Separation in Crossed E × B Fields with a Potential Well (a Review)
Аннотация
One of the relevant tasks of nuclear power industry is the reprocessing of spent nuclear fuel. Such processing implies the separation of actinides from uranium fission products. One of the processing methods can be plasma mass separation. In the last 10 years, research aimed at the development of various aspects related to plasma mass separation has been actively conducted at the Joint Institute for High Temperatures of the Russian Academy of Sciences. The article provides an overview of the main results of these studies in four areas: numerical calculations and analysis of separation schemes; generation of background plasma and formation of plasma potential distribution; plasma source for injection of a mixture of separated substances; and demonstration of the model substances separation.
278-287
Simulation of a Transverse–Longitudinal Discharge in a Supersonic Air Flow in the Hydrodynamic Approximation
Аннотация
Three-dimensional distributions of velocity, temperature and pressure in the supersonic air flow at M = 2, as well as the current density in the discharge initiated in it, are obtained. A direct current gas discharge of 10 A is considered in the hydrodynamic approximation within the channel model. The evolution of a transverse–longitudinal discharge is considered in the time range t up to 20 µs. It is shown that the discharge moves almost at the velocity of the main supersonic air flow disturbing it rather weakly. Based on the characteristic values of the current density and gas temperature of 8000–10 000 K obtained in the calculations, the electron density in the discharge channel is estimated as ne ~ 1016 cm–3. The field strength of E ~ 125 V/cm is estimated and the reduced field strength in the discharge channel E/N is about 30 Td. In the configuration of an aerodynamic model with shortened electrodes, the transition to the discharge phase fixed at their ends is shown.
288-295
Degradation Spectrum of Electrons in Methane
Аннотация
Numerical calculations are performed for the non-stationary non-equilibrium distribution function of electrons in gas methane CH4 under high-energy electrons with their initial energy 1 keV. The basic elementary processes of collisions of electrons with methane molecules have been considered. Expenditures of electron power into the various processes of molecule excitation, dissociation and ionization are computed so that to obtain the rates of interaction processes of electrons with methane molecules CH4.
296-302