Diffusion in a strongly coupled magnetized plasma

A first-principles study of diffusion in a strongly coupled one-component plasma in a magnetic field B is presented. As in a weakly coupled plasma, the diffusion coefficient perpendicular to the field exhibits a Bohm-like 1/B behavior in the strong-field limit but its overall scaling is substantially different. The diffusion coefficient parallel to the field is strongly affected by the field as well and also approaches a 1/B scaling, in striking contrast to earlier predictions.     

Photon processes in a strongly magnetized plasma

The photon-scattering process γe ^± → γe ^± is considered in strongly magnetized matter at arbitrary values of temperature and an arbitrary chemical potential. Simple expressions for the absorption coefficients in a strongly magnetized plasma are obtained in two limiting cases, that of a rarefied chargesymmetric plasma and that of a degenerate plasma. Astrophysical applications of the results obtained here are discussed.     

Propagation of axions in a strongly magnetized medium

The polarization operator of an axion in a degenerate gas of electrons occupying the ground-state Landau level in superstrong magnetic fields H≫H ₀=m _e ² c ³/eℏ=4.41×10¹³ G is investigated in a model with a tree-level axion-electron coupling. It is shown that a dynamic axion mass, which can fall within the allowed range of values 10⁻⁵ eV≲m _a≲10² eV, is generated under the conditions of strongly magnetized neutron stars. As a result, the dispersion relation for axions is appreciably different from that in a vacuum. Zh. éksp. Teor. Fiz. 115, 3–11 (January 1999)     

Nonlinear propagation of neutrinos in a strongly magnetized medium

The nonlinear propagation of an intense neutrino flux in an electron-positron plasma with equilibrium density and magnetic field inhomogeneities is considered. It is found that the neutrinos are nonlinearly coupled with electrostatic and electromagnetic disturbances due to weak Fermi interaction and ponderomotive forces. The process is governed by a Klein-Gordon equation for the neutrino flux and a wave equation for the plasma oscillations in the presence of the ponderomotive force of the neutrinos. This pair of equations is then used to derive a nonlinear dispersion relation which exhibits that nonthermal electrostatic and electromagnetic fluctuations are created on account of the energy density of the neutrinos. The relevance of our investigation to the anomalous absorption of neutrinos in a nonuniform magnetized medium is pointed out.     

Low ion velocity slowing down in a strongly magnetized plasma target

Ion projectile stopping at velocity smaller than target electron thermal velocity in a strong magnetic field, is investigated within a novel diffusion formulation (Dufty-Berkovsky), based on Green-Kubo integrands evaluated in magnetized one component plasma models, respectively framed on target ions and electrons. Analytic expressions are reported for slowing down orthogonal and parallel to an arbitrary large magnetic field, which are free from the usual uncertainties plaguing the standard perturbative derivations.     

Nonlocal theory of stimulated Raman backscattering in a strongly magnetized plasma

A nonlocal theory of stimulated Raman backscattering (BSRS) parametric instability of a large amplitude electromagnetic (EM) mode in a strongly magnetized plasma e.g., one encountered in a plasma filled backward wave oscillator, is reported. The EM mode is unstable to parametric instability in a magnetized plasma and decays into a Trivelpiece-Gould (TG) mode and a sideband EM mode. The growth rate of instability (Γ) scales proportional to three-fourth power of plasma density. For a typical BWO the growth rate is ∼10⁸ s^-1     

Neutrino interaction with strongly magnetized electron-positron plasma

A study is made of a complete set of neutrino-electron processes in a magnetized plasma. It is shown that processes involving neutrinos in the initial and final states ve ^? → ve ^? and v ? ve ^? e ⁺ have kinematic amplification in the ultrarelativistic limit. Relatively simple expressions are obtained for the probability and average neutrino energy-momentum loss which are convenient for quantitative analysis. It is observed that the total contribution of ve processes did not depend on the chemical potential of the magnetized electron-positron plasma.     

Modified Debye screening potential in a magnetized quantum plasma

The effects of quantum mechanical influence and uniform static magnetic field on the Shukla-Nambu-Salimullah potential in an ultracold homogeneous electron-ion Fermi plasma have been examined in detail. It is noticed that the strong quantum effect arising through the Bohm potential and the ion polarization effect can give rise to a new oscillatory behavior of the screening potential beyond the shielding cloud which could explain a new type of possible robust ordered structure formation in the quantum magnetoplasma. However, the magnetic field enhances the Debye length perpendicular to the magnetic field in the weak quantum limit of the quantum plasma.     

Nonstandard interactions in plasmon decay to a neutrino pair in a strongly magnetized medium

The neutrino luminosity of a stellar medium because of plasmon decay to a neutrino pair via nonstandard tensor interaction in a degenerate electron gas subjected to the effect of a magnetic field such strong that the electrons of the gas are in the lowest Landau level is calculated. Relative limits on nonstandard coupling constants are obtained from a comparison of the results of this calculation with the neutrino luminosity generated in the respective standard process proceeding under the same conditions.     

Production of electron-positron pairs by a photon propagating in a strongly magnetized thermal bath

The production of electron-positron pairs by a photon propagating in a thermal bath in both zero and strong (B ≫ 4.41 × 10¹³ G) magnetic fields has been considered. The mean free path has been calculated for the high-energy photon propagating through a thermodynamically equilibrium photon gas along the magnetic field lines so that the γ → e ⁻ e ⁺ decay is kinematically forbidden. It has been shown that the strong magnetic field suppresses the probability of the γγ′ → e ⁻ e ⁺ process. The analyzed process can be useful for analysis of possible mechanisms of the generation of the e ⁻ e ⁺ plasma in the regions of the polar caps of magnetars.     

Influence of strongly magnetized plasma on photon splitting

The photon splitting γ → γγ in a strongly magnetized medium of arbitrary temperature and chemical potential is considered. In comparison with the case of a pure magnetic field, a new photon splitting channel is shown to be possible below the electron-positron pair production threshold. The partial splitting amplitudes and probabilities are calculated by taking into account the photon dispersion in a strong magnetic field and a charge-symmetric plasma. An enhancement of the photon splitting probability compared to the case of a magnetic field without plasma has been found to be possible under certain conditions.     

Weak and electromagnetic mechanisms of neutrino-pair photoproduction in a strongly magnetized electron gas

Expressions for the power of neutrino radiation from a degenerate electron gas in a strong magnetic field are derived for the case of neutrino-pair photoproduction via the weak and electromagnetic interaction mechanisms (it is assumed that the neutrino possesses electromagnetic form factors). It is shown that the neutrino luminosity of a medium in the electromagnetic reaction channel may exceed substantially the luminosity in the weak channel. Relative upper bounds on the effective neutrino magnetic moment are obtained.     

Measurement of screening enhancement to nuclear reaction rates using a strongly magnetized and strongly correlated non-neutral plasma

An analogy is uncovered between the nuclear reaction rate in a dense neutral plasma and the energy equipartition rate in a strongly magnetized non-neutral plasma. In strong magnetic fields, cyclotron energy, like nuclear energy, is released only through rare close collisions between charges. The probability of such collisions is enhanced by plasma screening effects, just as in nuclear reactions. Enhancements of up to 10(10) are measured in simulations of cyclotron energy equipartition and are compared to the theory of screened nuclear reactions.     

Ion beam driven instabilities in unmagnetized and strongly magnetized plasmas

In this paper, the dissipative instabilities in the interaction of an ion beam with unmagnetized and strongly magnetized plasmas are investigated. In both cases, relevant dispersion equations of high-frequency and ion acoustic waves are obtained. In addition, the resonance frequencies and growth rates of the instabilities are derived. It is shown that the thermal motion of charged particles has positive effects on the resonance frequency but its influence on the growth rate of an instability depends on the plasma conditions. Although in all cases the collisions are found to have a stabilizing effect, it is shown that the dominant type of collisions (electron-neutral or ion-neutral collisions) depends on the frequency range. It is also indicated that the resonance frequency and the growth rate of an instability in the unmagnetized plasma is higher than in the strongly magnetized plasma for non-zero propagation angles.     

Molecular-dynamics simulations of cold antihydrogen formation in strongly magnetized plasmas

Employing a high-order symplectic integrator and an adaptive time-step algorithm, we perform molecular-dynamics simulations of antihydrogen formation, in a cold plasma confined by a strong magnetic field, over time scales of microseconds. Sufficient positron-antiproton recombination events occur to allow a statistical analysis for various properties of the formed antihydrogen atoms. Giant-dipole states are formed in the initial stage of recombination. In addition to neutral atoms, we also observe antihydrogen positive ions (H(+)), in which two positrons simultaneously bind to an antiproton.