Viktor P. Silin

Ion-acoustic turbulence and anomalous transport

Abstract We present results for the dynamics of evolution of non-linear state plasmas in a d.c. electric field which causes ion-acoustic turbulence (IAT). We look at (1) the time variation of the drift electron velocity and of the effective collision frequency, (2) features of the redistribution and heating of resonance ions, (3) the evolution of the spectral and angular distribution of turbulent pulsations, (4) processes of heating of the bulk of the particles. The results of an analytical IAT theory are compared with computer simulations. Special attention is paid to the theory of inhomogeneous plasmas with IAT. A self-consistent theory of anomalous transport is presented. We discuss the anisotropy of anomalous transport and the influence of non-Maxwellian particle velocity distributions on the transport processes. The electromagnetic properties, self-organization and hydrodynamic instability of plasmas with IAT are discussed.

4π-kink vortices in long Josephson junctions

Abstract The analytic theory of 4π-kinks in long Josephson junctions is presented. The laws for the velocity “quantized” spectrum of the different modes of the moving 4π-kinks nonlinear vortices are obtained. The discreteness of the velocity spectrum is dictated by the condition of the phase matching of the nonlinear state which does not permit breaking of the vortices due to the Cherenkov radiation.

On coherent harmonic bremsstrahlung in laser plasma

We give a theoretical description of the mechanisms underlying the generation of harmonics of plasma-warming radiation, which depend on the polarization of the latter. We show that there is a striking anomaly in the polarization of the harmonics in the presence of a low degree of circular polarization of the pump, and that harmonic generation efficiency increases. Variations in the polarization of the pump accompanying inverse bremsstrahlung absorption are discussed.

Weibel instability associated with inverse bremsstrahlung absorption of intense electromagnetic radiation

We investigate the Weibel instability in a plasma with a nonstationary three-temperature electron distribution generated by inverse bremsstrahlung of an intense elliptically polarized electromagnetic wave. We show that electron-ion collisions in this strong high frequency field are simultaneously the cause of the development of the instability and the reason it is suppressed. We find plasma and radiation parameters for which spontaneous quasistationary solenoidal electromagnetic fields can increase by many times.

Fast Josephson vortex

Abstract For the magnetically coupled waveguide and long Josephson junction we gave the analytic description of two separate velocity domains where the free motion of traveling vortex (2 π -kink) exists. The role of the mutual influence of waveguide and long Josephson junction is discussed. It is shown the possibility of the fast vortex motion with the velocity much larger than Swihart velocity of Josephson junction and close to the speed of light in the waveguide. The excitation of motion of such fast Josephson vortex is described.

TUNNEL IONIZATION AND MAGNETIC FIELD GENERATION

Abstract The possibility of the generation of a megagaus magnetic field in a plasma, creating at atom tunnel ionization in a high-power laser radiation field has been predicted.

Theory of ion-acoustic turbulence in plasma with anisotropically heated ions

A simple approximation extending the theory of ion-acoustic turbulence (IAT) is proposed. The approximation is based on the idea of efficient anisotropic ion heating in the Coulomb plasma model. The model makes it possible not only to employ the main results of the existing IAT theory without an assumption of strong ion collisions, but also to substantially extend them. The role of Cherenkov absorption of ion-acoustic waves is revealed. This absorption is caused by an anisotropic ion distribution in the new regimes of IAT that are related to its angular distribution and manifest themselves in electron and ion heating. A specific feature of the model is the finite time of existence of one of the IAT regimes under study.

High density current drive by high frequency radiation

A self-consistent theory is developed for current drive by intense radiation in the presence of the ion-acoustic instability. The spectrum of ion-acoustic turbulent noise generated by the driven current and concentrated in a limited cone of angles along the propagation direction of the wave is found. Excitation of the instability is accompanied by the establishment of an electron drift that is excited by the electromagnetic wave and has a velocity on the order of the ion acoustic speed. This current drive regime is realized over a wide range of intensities, as long as the region of turbulence in the angles of the acoustic wave vector is expanding. At yet higher intensities, the driven current increases in proportion to the intensity of the fundamental wave. Similar behavior is found for driven heat fluxes.

Gluing of Josephson vortices by Cherenkov-trapped Swihart waves

A theory of Josephson vortices-multikinks moving with a constant velocity is formulated for non-dissipative Josephson junctions on the basis of the Aubry-Volkov analytical model. Cherenkov trapping of Swihart waves by moving vortices is predicted. A description of the structure of vortices which is due to the waves trapped by them is given. It is predicted that the characteristic velocities of the moving vortices are discrete. This phenomenon is due to the structure of the Swihart waves trapped by the vortices. The concept of gluing of elementary Josephson vortices by Swihart waves in a coherently-phased, multivortex, structure is advanced.

Quantization of the motion and Cherenkov structure of a Josephson vortex

A generalization of the Sakai-Tateno-Pedersen model is proposed. This model is used to establish the existence of a discrete eigenvalue spectrum of the free-motion velocities of a Josephson vortex, or π kink, produced by the Cherenkov structure of extraordinary vortex-trapped Swihart waves having the spectrum (3.9). The dependence of the current across the Josephson junction on the vortex velocity was obtained, and, at comparatively high velocities, this was characterized by equidistant dips attributable to the Cherenkov resonant interaction of the vortex with Swihart waves.