Plasma Kinetic Theory Research Articles

Kinetic theory of a nonideal plasma: Dispersion relations

The kinetic theory of plasma based on the construction of propagators for the plasma particle distribution function is generalized to the case of a nonideal plasma. This theory is used for calculating the permittivity of a homogeneous nonideal plasma consisting of one species of ions neutralized by the polarized electron background. The dispersion relations are derived for ion-acoustic and low-frequency transverse waves in the plasma.

Long- and short-lived electrons with anomalously high collision rates in laser-ionized gases

Ultrashort broadband terahertz pulses are applied to probe the electron dynamics of gaseous Ar and O2 following ionization by an intense femtosecond laser pulse. The conductivity in the plasma center is extracted by a modified Wentzel-Kramers-Brillouin approach. It exhibits a nearly perfect Drude-like spectral shape and yields the temporal evolution of the free-electron density and collision rate. While the electron density in the Ar plasma remains nearly constant during the first 200ps after generation, it decays much faster in O2 due to dissociative recombination which is only possible in molecular plasmas. Adding a small amount of the electron scavenger SF6 to Ar reduces the electron lifetime in the plasma dramatically and allows us to determine the electron temperature to about 20,000K . Furthermore, anomalously high, metal-like electron collision rates of up to 25THz are found. Kinetic plasma theory substantially underestimates these rates pointing towards additional and more complex processes randomizing the total electronic momentum. Our results are relevant to both lightning control and generation of terahertz radiation by intense laser pulses in gases.

The Weibel instability in relativistic plasmas

Aims. We discuss the onset of the nonlinear stage of the electromagnetic Weibel instability in a relativistic plasma, and the process of current coalescence that follows this instability. The Weibel instability has been proposed as a possible source of the magnetic fields needed to explain the non-thermal synchrotron emission from gamma ray bursts. Methods. We present two different calculations of the nonlinear saturation of the Weibel instability: one based on a fluid model, and one using kinetic plasma theory. These approaches yield a similar result for the amplitude of the magnetic field at saturation. We then consider the further growth of the magnetic field due to the coalescence of current filaments, a process that has been observed in numerical simulations. Results. These calculations show that the exponential linear stage of the instability is terminated by trapping of the beam particles in the wave. The trapping leaves a magnetic field that acts as the seed field for further amplification through coalescence. Further field amplification is limited to magnetic fields on scales less than the effective plasma skin depth of a background plasma. We show that coalescence of current filaments thicker than a few times the skin depth proceeds at a exponentially slow rate. Conclusions. The amplitude of saturation is determined mostly by the plasma frequency of the hot (shocked) background plasma, which is usually dominated by the electrons. The typical field amplitude at this stage is almost independent of the mass of the beam particles. Further field amplification through current coalescence, a process that follows the exponential Weibel instability, “stalls” once the current filaments reach a size that is comparable to the skin depth of the background plasma. This process concentrates the currents, but the resulting field amplification is small. This implies that the resulting magnetic field energy density never reaches equipartition with the kinetic energy density of the heavy particle species (ions) in the incoming beams.

Interaction of picosecond laser pulses with a thin target

Interaction between a picosecond laser pulse of nonrelativistic intensity with a thin target is studied in terms of the kinetic theory of laser plasma, which is based on constructing propagators for the plasma particle distribution functions. Allowance is made for both the self-consistent plasma field and plasma particle correlations (collisions). The interaction causes charge separation in the target and strong heating of electrons.

High‐resolution electron temperature measurements using the plasma line asymmetry

In this paper, we present the first results of a new technique for measuring the electron temperature in the daytime ionosphere using the Arecibo incoherent scatter radar (ISR). The technique utilizes the plasma line component of the incoherent scatter spectrum. The difference in the up‐ and down‐shifted plasma line frequencies is related to the density and temperature of the ionosphere, as well as more minor effects resulting from photoelectrons, currents, and other sources. The shift is very small (the order of 1 kHz in a plasma line frequency of several MHz) but can be measured quite accurately with the coded long pulse plasma line technique. We compare the results to ion line measurements of the electron temperature, and the two independent techniques show good agreement. In addition to providing a measure of the electron temperature that is independent of the ion line, the approach allows for a sensitive test of kinetic plasma theory including a magnetic field, gives us the ability to study photoelectron populations and electron currents, and will allow us to constrain ion line fits in the bottomside (and possibly topside) regions to more accurately fit for composition.

A diffusion-controlled regime of cylindrical inductive discharges

A fluid-plasma model of diffusion-controlled cylindrical inductive discharges in an argon gas is presented. The plasma-field structure of the discharge obtained is completed by the interrelated behaviour of concentrations of charged particles, electron temperature, power absorbed on average by an electron, radial distribution of the components of the high-frequency field, of the Joule heating and of the high-frequency current density in the plasma. The self-consistency of the model and its validity over a wide pressure range (p = (0.05–5) Torr) is reached by involving detailed treatment of the electron energy balance, of the nonlinear processes in the charged particle balance and of the momentum equations. By accounting for the velocity dependence of the elastic electron–neutral collision frequency, concepts from the kinetic plasma theory are introduced in a fluid-plasma description of the discharge. The analysis of the results is in terms of changing gas pressure, power and frequency of the maintenance field. The changes of the parameters of the external coil due to the plasma loading in the coil are also discussed.

Kineticheskaya teoriya plazmi i gaza. Vzaimodejstvie moshnih lazernih impul'sov s plazmoj

Kineticheskaya teoriya plazmi i gaza. Vzaimodejstvie moshnih lazernih impul'sov s plazmoj

Self-Consistent Generation of Superthermal Electrons by Beam-Plasma Interaction

It has been known since the early days of plasma physics research that superthermal electrons are generated during beam-plasma laboratory experiments. Superthermal electrons (the kappa distribution) are also ubiquitously observed in space. To explain such a feature, various particle acceleration mechanisms have been proposed. However, self-consistent acceleration of electrons in the context of plasma kinetic theory has not been demonstrated to date. This Letter reports such a demonstration. It is shown that the collisionality, defined via the "plasma parameter" g=1/n(lambda(D)(3), plays a pivotal role. It is found that a small but moderately finite value of is necessary for the superthermal tail to be generated, implying that purely collisionless (g=0) Vlasov theory cannot produce a superthermal population.

Stochastic heating of dust particles with fluctuating charges

The results from the kinetic theory of dusty plasmas, which consistently takes into account the charging and Coulomb collisions of plasma particles with dust, are used to show that, due to the dust charge fluctuations in dust-dust interactions, energy is not conserved in the subsystem of dust particles. The growth rate of the dust mean energy is found proportional to the mean square dust charge fluctuations, as physically expected.

On the Vlasov Limit for Systems of Nonlinearly Coupled Oscillators without Noise

We discuss the application to systems of coupled nonlinear oscillators of methods originally developed for the Vlasov-Poisson equations of plasma kinetic theory. These methods lead to a simple but rigorous derivation of the infinite-oscillator limit for the well-known Kuramoto model, and also to a compact proof of global existence and uniqueness of solutions to the resulting Kuramoto-Sakaguchi equations. Vlasov-limit techniques can also be adapted to prove a central limit theorem for statistical ensembles of systems of oscillators. However, we emphasize that the noiseless Kuramoto model itself is strictly deterministic, and that the Kuramoto-Sakaguchi equations can be formulated without any reference to a stochastic distribution of oscillator frequencies.

Global classical solution of the Vlasov–Maxwell–Landau system near Maxwellians

We consider a classical model in the kinetic theory of plasma—the Vlasov–Maxwell–Landau system. Global in time classical solutions near Maxwellians are constructed for hard potential and soft potential, i.e., γ⩾−1. The construction of global solution is based on an energy method. Meanwhile, global classical solutions of the Vlasov–Poisson–Landau system near Maxwellians for γ⩾−1 and the exponential decay of such solutions are obtained.

Kinetic susceptibility and transport theory of collisional plasmas.

A system of nonlocal electron transport equations for electrostatic perturbations in (omega,k) space in a high-Z plasma is derived from the Fokker-Planck equation for arbitrary relations between the time, space, and collisionality scales. The closed scheme for obtaining the longitudinal plasma susceptibility epsilon(omega,k) in the entire (omega,k) plane is proposed. Regions in the (omega,k) plane have been mapped for problems such as the relaxation of the local temperature enhancement with a time-dependent heat conductivity. The electron dielectric permittivity has been calculated over the entire range of parameters, including the transition region between Vlasov and Fokker-Planck equation solutions.

Kinetic theory of rarefied plasma: The effective action method

A kinetic theory of rarefied plasma that is based on the construction of propagators for distribution functions is developed. The feature of this theory, which is physically equivalent to the standard kinetic theory, is that propagators being constructed for distribution functions are themselves dependent on these distribution functions.

Is the classical two-term approximation of electron kinetic theory satisfactory for swarms and plasmas?

The ‘two-term’ approximation (representation of the electron distribution by the first two terms of an expansion in spherical harmonics in velocity space) continues to occupy a central role in the low-temperature plasma physics literature, in spite of the mass of evidence illustrating its inadequacy in the swarm (free diffusion) limit for many molecular gases. Part of the problem lies in the failure of many authors to specify quantitatively what they mean when they say that the two-term approximation is ‘acceptable’. Thus for example, an error of 10% in transport coefficients may well be acceptable in many plasma applications, but for analysis of highly accurate swarm experiments to compare with ab initio and beam-derived cross-sections, 0.1% or less is required, making ‘multi-term’ analysis mandatory. While reconciliation of the swarm and plasma literature along the lines of two different accuracy regimes may thus be possible, we dispute claims that the two-term approximation is generally satisfactory for inversion of swarm experiment data to obtain electron impact cross-sections. The unsatisfactory nature of other assumptions implicit in much of the modern plasma kinetic theory literature is also discussed.

Contributions of Yuri L. Klimontovich to the kinetic theory of nonideal plasmas

AbstractWe give a short summary of live and work of Yuri L. Klimontovich (1924–2002), in particular we discuss his work on nonideal plasma physics. (© 2003 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Plasma Astrophysics: Kinetic Processes in Solar and Stellar Coronae, Second Edition

A collision‐less plasma is an ionized fluid that is so hot and tenuous that interactions between individual particles are unimportant. In such a plasma, electric and magnetic fields mediate interactions among particles, and fundamental physics is addressed by kinetic theories that describe not only the spatial and temporal variations of the medium, but also its velocity‐space properties.The outer corona of our Sun and the outer coronae of many stars are collision‐less plasmas. Thus, the preface of Plasma Astrophysics begins. “This textbook is intended as an introduction to the physics of solar and stellar coronae, emphasizing kinetic plasma processes.” But the content extends well beyond the stated purview. In fact, many plasmas of the universe are collision‐less, including many space plasmas—those that are subject to in situ measurements by spacecraft—and a wide variety of astrophysical plasmas. Thus, although the parameters and phenomena that characterize the collision‐less plasmas of space, the solar corona, and astrophysics are often very different, the physics in each case derives from the same fundamental kinetic plasma theory.

Drift-wave instability excited by field-aligned ion flow velocity shear in the absence of electron current.

The drift wave is observed to be destabilized by a magnetic-field-aligned ion flow velocity shear in the absence of field-aligned electron drift flow in laboratory experiments using a concentrically three-segmented plasma source. The fluctuation amplitude increases with increasing a shear strength, but the instability is found to be gradually stabilized when the shear strength exceeds a critical value. The destabilizing and stabilizing mechanisms are well explained by a plasma kinetic theory including the effect of radial density gradient.

New microscopic and macroscopic variables in dustyplasmas

The kinetic theory of dusty plasmas, in which the absorption ofelectrons and ions by dust particles is the dominating interactionprocess, is derived from first principles. The charging process isshown to imply a considerable modification of properties incomparison with usual plasmas. Not only the electric charge, butalso the mass, the angular momentum and the inner energy of thedust particles are new dynamic variables. Their influence on thekinetic behaviour of dusty plasmas is also considered.

Covariant linear response theory of relativistic QED plasmas

We start from the QED Lagrangian to describe a charged many-particle system coupled to the radiation field. A covariant density matrix approach to kinetic theory of QED plasmas, subjected to a strong external electro-magnetic field has recently been developed (Theor. Math. Phys. 131 (2002) 812; Theor. Math. Phys. 132 (2002) 1026). We use the hyperplane formalism in order to perform a manifest covariant quantization and to implement initial correlations to the solution of the Liouville-von Neumann equation. A perturbative expansion in orders of the fine structure constant for the correlation functions as well as the statistical operator is applied. The non-equilibrium state of the system is given within generalized linear response theory. Expressions for the susceptibility tensor, describing the plasma response, are calculated within different approximations, like the RPA approximation or considering collisions within the Born-approximation. In particular, the process of relativistic inverse bremsstrahlung in a plasma is discussed.

Kinetic theory of dusty plasmas. IV. Distribution and fluctuations of dust charges

The recent results of the kinetic theory of dusty plasmas [V. N. Tsytovich and U. de Angelis, Phys. Plasmas 6, 1093 (1999)] are used to investigate the distribution and fluctuations of the dust charges in dusty plasmas. It is shown that the charge fluctuations induced by dust discreteness can be larger than the fluctuations due to electron and ion discreteness. A new Lorentz form for the regular part of the dust charge distribution is found.