arXiv subjects

J. Ortner

Publications and source records attributed to J. Ortner.

17 recordsLinked to original sources

arXiv2001

Evolution of induced axial magnetization in a two-component magnetized plasma

In this paper, the evolution of the induced axial magnetization due to the propagation of an electromagnetic (em) wave along the static background magnetic field in a two-component plasma has been investigated using the Block equation. The evolution process induces a strong magnetic anisotropy in the plasma medium, depending nonlinearly on the incident wave amplitude. This induced magnetic anisotropy can modify the dispersion relation of the incident em wave, which has been obtained in this paper. In the low frequency Alfven wave limit, this dispersion relation shows that the resulting phase velocity of the incident wave depends on the square of the incident wave amplitude and on the static background magnetic field of plasma. The analytical results are in well agreement with the numerically estimated values in solar corona and sunspots.

physics.plasm-ph↗

arXiv1999

Relativistic photoelectron spectra in the ionization of atoms by elliptically polarized light

Relativistic tunnel ionization of atoms by intense, elliptically polarized light is considered. The relativistic version of the Landau-Dykhne formula is employed. The general analytical expression is obtained for the relativistic photoelectron spectra. The most probable angle of electron emission, the angular distribution near this angle, the position of the maximum and the width of the energy spectrum are calculated. In the weak field limit we obtain the familiar non-relativistic results. For the case of circular polarization our analytical results are in agreement with recent derivations of Krainov [V.P. Krainov, J. Phys. B, {\bf 32}, 1607 (1999)].

physics.atom-ph↗

arXiv1999

Dynamic structure factor and collective excitations of neutral and Coulomb fluids

The dynamic sructure factor as the basic quantity describing the collective excitations in a fluid is considered. We consider the cases of neutral and Coulombic fluids. The classical method of moments is applied to construct the dynamic structure factor satisfying all known sum rules. An interpolational formula is found which expresses the dynamic characteristics of a classical or quantum fluid system in terms of its static correlation parameters. The analytical results based on the theory of moments are compared with Molecular dynamics data for various model systems.

physics.plasm-ph↗

arXiv1999

Semiclassical dynamics and time correlations in two-component plasmas

The semiclassical dynamics of a charged particle moving in a two-component plasma is considered using a corrected Kelbg pseudopotential. We employ the classical Nevanlinna-type theory of frequency moments to determine the velocity and force autocorrelation functions. The constructed expressions preserve the exact short and long-time behavior of the autocorrelators. The short-time behavior is characterized by two parameters which are expressable through the plasma static correlation functions. The long-time behavior is determined by the self-diffusion coefficient. The theoretical predictions are compared with the results of semiclassical molecular dynamics simulation.

physics.plasm-ph↗

arXiv1999

Relativistic semiclassical approach in strong-field nonlinear photoionization

Nonlinear relativistic ionization phenomena induced by a strong laser radiation with elliptically polarization are considered. The starting point is the classical relativistic action for a free electron moving in the electromagnetic field created by a strong laser beam. The application of the relativistic action to the classical barrier-suppression ionization is briefly discussed. Further the relativistic version of the Landau-Dykhne formula is employed to consider the semiclassical sub-barrier ionization. Simple analytical expressions have been found for: (i) the rates of the strong-field nonlinear ionization including relativistic initial and final state effects; (ii) the most probable value of the components of the photoelectron final state momentum; (iii) the most probable direction of photoelectron emission and (iv) the distribution of the photoelectron momentum near its maximum value.

physics.atom-ph↗

arXiv1999

Electric microfield distribution in two-component plasmas. Theory and Simulations

The distribution of the electric microfield at a charged particle moving in a two-component plasma is calculated. The theoretical approximations are obtained via the parameter integration technique and using the screened pair approximation for the generalized radial distribution function. It is shown that the two-component plasma microfield distribution shows a larger probability of high microfield values than the corresponding distribution of the commonly used OCP model. The theory is checked by quasiclassical molecular-dynamics simulations. For the simulations a corrected Kelbg pseudopotential has been used.

physics.plasm-ph↗

arXiv1999

Ground-state energy of a high-density electron gas in a strong magnetic field

The high-density electron gas in a strong magnetic field B and at zero temperature is investigated. The quantum strong-field limit is considered in which only the lowest Landau level is occupied. It is shown that the perturbation series of the ground-state energy can be represented in analogy to the Gell-Mann Brueckner expression of the ground-state energy of the field-free electron gas. The role of the expansion parameter is taken by $r_B= (2/3 π^2) (B/m^2) (\hbar r_S/e)^3$ instead of the field-free Gell-Mann Brueckner parameter r_s.

cond-mat↗

arXiv1999

Second virial coefficient for the Landau diamagnetism of a two component plasma

This paper investigates the density expansion of the thermodynamic properties of a two component plasma under the influence of a weak constant uniform magnetic field. We start with the fugacity expansion for the Helmholtz free energy. The leading terms with respect to the density are calculated by a perturbation expansion with respect to the magnetic field. We find a new magnetic virial function for a low density plasma which is exact in quadratic order with respect to the magnetic field. Using these results we compute the magnetization and the magnetic susceptibility.

physics.plasm-ph↗

arXiv1999

The use of relativistic action in strong-field nonlinear photoionization

Nonlinear relativistic ionization phenomena induced by a strong linearly polarized laser field are considered. The starting point is the classical relativistic action for a free electron moving in the electromagnetic field created by a strong laser beam. This action has been used to calculate semiclassical transition rates. Simple analytical expressions for the ionization rate, the photoelectron emission velocity and for the drift momentum distribution of the photoelectron have been found. The analytical formulas apply to nonrelativistic bound systems as well as to initial states with an energy corresponding to the upper boundary of the lower continuum and to the tunnel as well as the multiphoton regime. In the case of a nonrelativistic bound system we recover the Keldysh formula for the ionization rate. Relativistic effects in the initial state lead to a weak enhancement of the rate of sub-barrier ionization and to the appearance of a nonzero photoelectron leaving velocity.

physics.atom-ph↗

arXiv1999

Equation of states for classical Coulomb systems. The use of Hubbard-Schofield approach

An effective method based on Hubbard-Schofield approach [Phys. Lett. A {\bf 40}, 245 (1972)] is developed to calculate the free energy of classical Coulomb systems. This method significantly simplifies the derivation of the cluster expansion. A diagrammatic representation of the cluster integrals is proposed. Simple rules providing the leading order in density $n$ of each diagrammatic contribution are found. We calculate the $n^3$ contribution and recover the results at the order $n^{5/2}$ obtained by the traditional method of resummation of diverging Mayer bonds.

physics.class-ph↗

arXiv1999

Electromagnetic modes in cold magnetized strongly coupled plasmas

The spectrum of electromagnetic waves propagating in a strongly coupled magnetized fully ionized hydrogen plasma is found. The ion motion and damping being neglected, the influence of the Coulomb coupling on the electromagnetic spectrum is analyzed.

physics.plasm-ph↗

arXiv1999

Quasiclassical Theory and Simulations of Strongly Coupled Plasmas

A survey on the dynamical and thermodynamical properties of plasmas with strong Coulomb interactions in the quasi-classical density-temperature region is given. First the basic theoretical concepts describing nonideality are discussed. The chemical picture is introduced. It is shown that the nonideal plasma subsystem of the free charges has a rather large quasi-classical regime, where the quantum effects yield only corrections to the merely classical dynamics. The plasma of free charges may be described by effective potentials which incorporate quantum effects in an approximative way. The simplest effective potentials are only space-dependent, more advanced methods include momentum-dependent interactions. On the basis of these potentials analytical results are derived and simulation methods are developed. It is shown that effective potentials are appropriate for the description of thermodynamical as well as collective properties.

physics.plasm-ph↗

arXiv1999

The Nonlinear Debye-Onsager Relaxation Effect in Weakly Ionized Plasmas

A weakly ionized plasma under the influence of a strong electric field is considered. Supposing a local Maxwellian distribution for the electron momenta the plasma is described by hydrodynamic equations for the pair distribution functions. These equations are solved and the relaxation field is calculated for an arbitrary field strength. It is found that the relaxation effect becomes lower with increasing strength of the electrical field.

physics.plasm-ph↗

arXiv1999

Quasi-classical Molecular Dynamics Simulations of the Electron Gas: Dynamic properties

Results of quasi-classical molecular dynamics simulations of the quantum electron gas are reported. Quantum effects corresponding to the Pauli and the Heisenberg principle are modeled by an effective momentum-dependent Hamiltonian. The velocity autocorrelation functions and the dynamic structure factors have been computed. A comparison with theoretical predictions was performed.

physics.plasm-ph↗

arXiv1999

Do correlations create an energy gap in electronic bilayers? Critical analysis of different approaches

This paper investigates the effect of correlations in electronic bilayers on the longitudinal collective mode structure. We employ the dielectric permeability constructed by means of the classical theory of moments. It is shown that the neglection of damping processes overestimates the role of correlations. We conclude that the correct account of damping processes leads to an absence of an energy gap.

cond-mat.str-el↗

arXiv1998

Correlation energy of an electron gas in strong magnetic fields at high densities

The high-density electron gas in a strong magnetic field B and at zero temperature is investigated. The quantum strong-field limit is considered in which only the lowest Landau level is occupied. It is shown that the perturbation series of the ground-state energy can be represented in analogy to the Gell-Mann Brueckner expression of the ground-state energy of the field-free electron gas. The role of the expansion parameter is taken by r_B= (2/3 π^2) (B/m^2) (\hbar r_s /e)^3 instead of the field-free Gell-Mann Brueckner parameter r_s. The perturbation series is given exactly up to o(r_B) for the case of a small filling factor for the lowest Landau level.

cond-mat↗

arXiv1998

Equation of state of a strongly magnetized hydrogen plasma

The influence of a constant uniform magnetic field on the thermodynamic properties of a partially ionized hydrogen plasma is studied. Using the method of Green' s function various interaction contributions to the thermodynamic functions are calculated. The equation of state of a quantum magnetized plasma is presented within the framework of a low density expansion up to the order e^4 n^2 and, additionally, including ladder type contributions via the bound states in the case of strong magnetic fields (2.35*10^{5} T << B << 2.35*10^{9} T). We show that for high densities (n=10^{27-30} m^{-3}) and temperatures T=10^5 - 10^6 K typical for the surface of neutron stars nonideality effects as, e.g., Debye screening must be taken into account.

physics.plasm-ph↗