On Electron Concentration Distribution along the Radius of the Positive Column of a Glow Discharge in Electronegative Gases

It is shown in this paper that the form of the electron concentration distribution along the radius of the positive column in an oxygen discharge depends on the relative concentration of negative ions α = n_-/n_e in the plasma. It is found that in discharges in electronegative gases everywhere along the radius of the positive column, where α > 10, the electron concentration is equal to its value on the tube axis (plane electron distribution along the radius of the positive column). It is shown that an increase of the discharge current leads to the decrease of α and to the change of the distribution of profile n_e from plane to parabolic. However, weak laminar oxygen pumping along the positive column leads to more plane an electron concentration distribution because an increase of the negative ions concentration takes place. It is induced by the decrease of oxygen atoms density on account of their carrying out by the flow.     

Predicted thermal superluminescence in low-pressure air

It is shown that due to the dissociation of the molecular oxygen it is possible to obtain inverted population in low pressure air by heating. As a result of the quenching of the corresponding levels of the atomic oxygen the thermal superluminescent radiation is generated. It has been found that the threshold of the overpopulation is exceeded at the air temperature 2300 K ≲ T ≲ 3000 K. Using this effect a possible mechanism for the generation of the flashes of the radiation in air observed on the airframe of the space shuttle during its descent and reentry in the atmosphere is suggested.     

Red flashes in air

A red flash in a low-pressure air discharge is experimentally studied. Optical radiation, double electric probes, and the electric current of the pulsed plasma that is generated against a low-current stationary discharge are measured. The experimental data are analyzed.     

Transformation of acoustic waves in upper atmosphere

The transformation of acoustic waves into electromagnetic oscillations in the plasma of the upper atmosphere is analyzed. It is demonstrated that acoustic oscillations in ionosphere in the presence of the gradients of gas temperature and electron concentration lead to plasma vortices that provide the generation of electromagnetic waves.     

Accounting for Fluid Rheology in the Hydrophobization Model of Relative Permeability Hysteresis

A complex mathematical model of relative permeability hysteresis is developed based on percolation theory. The model takes into account the change in the surface properties of the pore space and the rheology of percolating fluids during the transition from drainage to imbibition, which gives rise to hysteresis. It is shown that accounting for the change in the rheology of percolation fluids, along with accounting for the hydrophobization of the surface of the pore space, provides a better agreement between the calculated and experimental curves of relative permeabilities.     

Formation of red sprites

The properties of red sprites that are generated in the ionosphere at an altitude of 100 km are considered. A process that leads to the formation of such plasma objects is proposed. It is demonstrated that sprites are generated by acoustic waves that give rise to vortices and gas breakdown in the presence of strong gradients of gas temperature and electron density.     

A study of acoustic waves generated by the shock wave of an antihail gun

The processes of propagation of a shock wave generated by an antihail gun are analyzed. It is shown that a shock wave can reach an altitude of 100 km. The measurement results of the time dependence of variation in acoustic intensity and sound frequency for a vertically propagating shock wave are presented.     

Gas-discharge acoustically induced laser

The generation of superluminescent flashes from a positive argon column induced by an acoustic wave upon a stepwise transition of the high-pressure gas discharge from the noncontracted state to the contracted state is considered. The conditions for the acoustically induced population inversion in the plasma column are described. The creation of a gas-discharge acoustically induced laser is proposed.     

Acoustic wave amplification in a plasma of a molecular gaseous discharge

From the experimental investigation of sound propagation in a gaseous discharge, it is established that, in a stationary diffusive discharge in nitrogen, sound amplification takes place according to the linear theory, whereas a sharp transverse constriction of the discharge leads to a sharp, jump-like increase in the amplification factor because of the steep dependence of the relaxation constant of a vibrationally excited molecule on the gas temperature. This result agrees well with the nonlinear theory of sound amplification in a nonequilibrium molecular gas. It is shown that the introduction of oxygen in the nitrogen discharge leads to an increase in the sound amplification factor in the plasma, because the constant of the vibrational relaxation of an excited nitrogen molecule by oxygen is two orders of magnitude greater than the constant of relaxation of nitrogen by nitrogen.     

Gas-flow-controlled gas-discharge laser

The creation of population inversion in the gas discharge with a turbulent gas flow due to the transformation of a positive column from the state of a uniform noncontracted discharge to the contracted state at a relatively high pressure is considered. The process under study is accompanied by a superluminescence flash. Based on the results obtained, a gas-discharge laser controlled by the gas flow can be created.