T. V. Losseva

Shock waves in charge-varying dusty plasmas and the effect of electromagnetic radiation

Nonlinear electrostatic wave structures in dusty plasmas in the presence of electromagnetic radiation are investigated. The dust charge variation is assumed to be caused by microscopic electron and ion currents at the grains as well as photoelectric current of electrons. Calculations of electromagnetic radiation effects are performed for the case of solar radiation spectrum in the vicinity of the earth. The exact solutions of the nonlinear equations, describing variable-charge dust grains, Boltzmann electrons, and inertial ions, are obtained in the form of steady-state shocks. The conditions for their existence are found. The dissipation in such shock waves originates from the process of dust charging. The possibility of observation of shock waves related to the dust charging process in the presence of electromagnetic radiation in active rocket experiments which involve the release of some gaseous substance in near-earth space is discussed.

Dust ion-acoustic shock-wave structures: Theory and laboratory experiments

An evolutionary theoretical model is developed that describes dust ion-acoustic shock waves in dusty plasma consisting of ions (treated in the hydrodynamic approximation), Boltzmann electrons, and variable-charge dust grains. Account is taken not only of ionization, absorption, momentum loss by electrons and ions in collisions with dust grains, and gas-kinetic pressure effects but also of the processes peculiar to laboratory plasmas. It is shown that the model is capable of describing all the main experimental results on dust ion-acoustic shock waves [Q.-Z. Luo et al., Phys. Plasmas 6, 3455 (1999); Y. Nakamura et al., Phys. Rev. Lett., 83, 1602 (1999)].

Dissipative processes during the propagation of nonlinear dust ion-acoustic perturbations

A comparative analysis of various dissipative processes occurring on ion-acoustic time scales during the excitation and propagation of nonlinear dust ion-acoustic perturbations in a complex (dusty) plasma is performed in terms of a purely kinetic approach and a hydrodynamic approach. It is found that the most important dissipative processes are the charging of dust grains, the absorption of ions by grains, the transfer of the ion momentum to the grains, and Landau damping. The damping rate of dust ion-acoustic waves is derived based on a purely kinetic approach to describing complex plasmas; this makes it possible to eliminate all of the earlier contradictions in the description of Landau damping in a complex plasma. The relative roles played by dissipative processes in different laboratory experiments with dusty plasmas are compared.

Evolution of weakly dissipative hybrid dust ion-acoustic solitons in complex plasmas

Possibility for hybrid ion-acoustic solitons to exist in complex (dusty) plasmas is investigated. Rarefactive solitonlike perturbations are damped and slowed down, mainly due to the plasma absorption and ion scattering on microparticles. Nevertheless, the amplitude of the evolving perturbation at any moment is given by the amplitude of the “conservative” soliton for the corresponding Mach number (so far as the conservative soliton exists). That property allows us to interpret the evolving rarefactive perturbation as a “weakly dissipative” hybrid dust ion-acoustic soliton. The weakly dissipative hybrid dust ion-acoustic solitons can be studied experimentally in laboratory complex plasmas.

Evolution of perturbation in charge-varying dusty plasmas

The nonstationary problem of the evolution of perturbation and its transformation into nonlinear wave structure in dusty plasmas is considered. For this purpose two one-dimensional models based on a set of fluid equations, Poisson’s equation, and a charging equation for dust are developed. The first (simplified) model corresponds to the case [Popel et al., Phys. Plasmas 3, 4313 (1996)] when exact steady-state shock wave solutions can exist. This simplified model includes variable-charged dust grains, Boltzmann electrons, and inertial ions. The second (ionization source) model takes into account the variation of the ion density and the ion momentum dissipation due to dust particle charging as well as the source of plasma particles due to ionization process. The computational method for solving the set of equations which describe the evolution in time of a nonlinear structure in a charge-varying dusty plasma is developed. The case of the evolution of an intensive initial nonmoving region with a constant enh...

Dissipative processes and dust ion-acoustic shocks in a Q machine device

A comparative analysis of the most important dissipative processes occurring during the excitation and propagation of dust ion-acoustic shocks in a Q machine device, among which are the charging of dust grains, the absorption of ions by grains, the transfer of the ion momentum to the grains, and Landau damping, is performed. The relative roles played by dissipative processes in different types of laboratory experiments with complex plasmas are estimated.

Ion-acoustic solitons in dusty plasma

The dynamics of dust ion-acoustic solitons is analyzed in a wide range of dusty plasma parameters. The cases of both a positive dust grain charge arising due to the photoelectric effect caused by intense electromagnetic radiation and a negative grain charge established in the absence of electromagnetic radiation are considered. The ranges of plasma parameters and Mach numbers in which “conservative” (nondissipative) solitons can exist are determined. It is shown that, in dusty plasma with negatively charged dust grains, both compression and rarefaction solitons can propagate, whereas in plasma with positively charged dust grains, only compression solitons can exist. The evolution of soliton-like compression and rarefaction perturbations is studied by numerically solving the hydrodynamic equations for ions and dust grains, as well as the equation for dust grain charging. The main dissipation mechanisms, such as grain charging, ion absorption by dust grains, momentum exchange between ions and dust grains, and ion-neutral collisions are taken into account. It is shown that the amplitudes of soliton-like compression and rarefaction perturbations decrease in the course of their evolution and their velocities (the Mach numbers) decrease monotonically in time. At any instant of time, the shape of an evolving soliton-like perturbation coincides with the shape of a conservative soliton corresponding to the current value of the Mach number. It is shown that, after the interaction between any types of soliton-like perturbations, their velocities and shapes are restored (with a certain phase shift) to those of the corresponding perturbations propagating without interaction; i.e., they are in fact weakly dissipative solitons.

Nonquasineutral relativistic current filaments and their X-ray emission

Nonquasineutral electron current filaments with the azimuthal magnetic field are considered that arise due to the generation of electron vorticity in the initial (dissipative) stage of evolution of a current-carrying plasma, when the Hall number is small (σB/enec ≪ 1) because of the low values of the plasma conductivity and magnetic field strength. Equilibrium filamentary structures with both zero and nonzero net currents are considered. Structures with a zero net current type form on time scales of t < tsk = (r0ωpe/c)2tst, where tsk is the skin time, tst is the typical time of electron-ion collisions, and r0 is the radius of the filament. It is shown that, in nonquasineutral filaments in which the current is carried by electrons drifting in the crossed electric (Er) and magnetic (Bθ) fields, ultrarelativistic electron beams on the typical charge-separation scale rB = B/(4πene) (the so-called magnetic Debye radius) can be generated. It is found that, for comparable electron currents, the characteristic electron energy in filaments with a nonzero net current is significantly lower than that in zero-net-current filaments that form on typical time scales of t < tsk. This is because, in the latter type of filaments, the oppositely directed electron currents repel one another; as a result, both the density and velocity of electrons increase near the filament axis, where the velocities of relativistic electrons are maximum. Filaments with a zero net current can emit X rays with photon energies ℏ ω up to 10 MeV. The electron velocity distributions in filaments, the X-ray emission spectra, and the total X-ray yield per unit filament length are calculated as functions of the current and the electron number density in the filament. Analytical estimates of the characteristic lifetime of a radiating filament and the typical size of the radiating region as functions of the plasma density are obtained. The results of calculations are compared with the available experimental data.

Formation of shocks related to dust-particle charging in complex plasmas

The nonstationary problem of the evolution of perturbation and its transformation into nonlinear wave structure in complex plasmas (multicomponent plasmas containing ions, electrons, charged microspheres or dust grains, and neutral gas) is considered. For this purpose, the model, which takes into account the variation of ion density and the ion-momentum dissipation due to dust-particle charging, as well as the source of plasma particles due to the ionization process, is developed. The model is appropriate for the description of laboratory experiments in complex plasmas and contains all basic mechanisms responsible for the formation of a new kind of shock waves which is related to the anomalous dissipation due to the dust-particle charging process. The consideration on the basis of this model allows us to obtain shock structures as a result of evolution of an initial perturbation and to explain the experimental value of the width of the ion acoustic shock-wave front, as well as the shock-wave speed. The solution of the problem of the evolution of perturbation and its transformation into a shock wave in complex plasmas opens up possibilities for description of the real phenomena like supernova explosions, as well as of the laboratory and active space and geophysical experiments.

Localization of Magnetized Electrons in Current Filaments as a Fundamental Cause of Coulomb Explosion

Mechanisms for generating current filaments in a dense plasma under the action of focused laser pulses and in a Z-pinch configuration are discussed. The main properties of current filaments with a zero and nonzero electron vorticity Ωe=B−(c/e)∇×pe that originate at magnetic fields in the range 4πnemec2≪B2≪4πnimic2 are investigated under the conditions of Coulomb explosion at currents below the ion Alfvén current. A study is made of the equilibrium configurations of nonquasineutral current filaments in a purely longitudinal (Bz) and a purely azimuthal (Bθ) magnetic field and also in a more general case of a helical magnetic field, having two components, under conditions such that the charge separation occurs on a spatial scale on the order of the magnetic Debye radius rB ≃ |B|/(4πene. It is shown that strong electric fields generated in the current filaments are comparable in magnitude to the atomic field and are capable of accelerating ions to energies of several tens of megaelectronvolts. The ion dynamics in strong electric fields of the filaments is calculated numerically and is shown to lead to the formation of collisionless shock waves on time scales on the order of several inverse ion plasma frequencies ωpi−1. The possible formation of current filaments on different spatiotemporal scales is considered.