Electromagnetic Dispersion Relation Research Articles

Comment on “Kinetic theory of surface waves in plasma jets” [Phys. Plasmas 9, 701 (2002)

It is shown that the dispersion relation of electromagnetic surface waves propagating on the interface between a vacuum and drifting Maxwellian plasmas derived in recent work [Phys. Plasmas 9, 701 (2002)] is incorrect. Correct electromagnetic and electrostatic dispersion relations are obtained.

Surface waves in anisotropic Maxwellian plasmas

Dispersion relation of electromagnetic surface waves propagating on the interface between a vacuum and anisotropic Maxwellian plasmas is derived from Vlasov–Maxwell equations. By taking the limit of infinite speed of light in the electromagnetic dispersion relation, we derived dispersion relation of electrostatic surface waves, and we find that plasmas with equilibrium distribution f0α=(mα∕2πTα)exp{−[mα(vx2+vy2)]∕2Tα}δ(vz) (α=e,i; electrons and ions), where the z direction is normal to the interface, can be unstable to perturbations of ion-acoustic surface wave type.

Calculation of pitch angle and energy diffusion coefficients with the PADIE code

We present a new computer code (PADIE) that calculates fully relativistic quasi‐linear pitch angle and energy diffusion coefficients for resonant wave‐particle interactions in a magnetized plasma. Unlike previous codes, the full electromagnetic dispersion relation is used so that interactions involving any linear electromagnetic wave mode in a predominantly cold plasma can be addressed for any ratio of the plasma‐frequency to the cyclotron frequency ωpe/∣Ωe∣. The code can be applied to problems in astrophysical, magnetospheric, and laboratory plasmas. The code is applied here to the Earth's radiation belts to calculate electron diffusion by whistler mode chorus, electromagnetic ion cyclotron (EMIC), and Z mode waves. The high‐density approximation is remarkably good for electron diffusion by whistler mode chorus for energies E ≥ 100 keV, even for ωpe/∣Ωe∣ ≈ 2 but underestimates diffusion by orders of magnitude at low energies (∼10 keV). When a realistic angular spread of propagating waves is introduced for EMIC waves, electron diffusion at ∼0.5 MeV is only slightly reduced compared with the assumption of field‐aligned propagation, but at ∼5 MeV, electron diffusion at pitch angles near 90° is reduced by a factor of 5 and increased by several orders of magnitude at pitch angles 30°–80°. Scattering by EMIC waves should contribute to flattening of the distribution function. The first results for electron diffusion by Z mode waves are presented. They show that unlike the whistler and EMIC waves, energy diffusion exceeds pitch angle diffusion over a broad range of pitch angles less than 45°. The results suggest that Z mode waves could provide a significant contribution to electron acceleration in the radiation belts during storm times.

Collective electromagnetic modes for beam-plasma interaction in the wholekspace

We investigate the linear stability of the system formed by an electron beam and its return plasma current within a general framework, namely, for any orientation of the wave vector k with respect to the beam and without any a priori assumption on the orientation of the electric field with respect to k . We apply this formalism to three configurations: cold beam and cold plasma, cold beam and hot plasma, and cold relativistic beam and hot plasma. We proceed to the identification and systematic study of the two branches of the electromagnetic dispersion relation. One pertains to Weibel-like beam modes with transverse electric proper waves. The other one refers to electric proper waves belonging to the plane formed by k and the beam, it divides between Weibel-like beam modes and a branch sweeping from longitudinal two-stream modes to purely transverse filamentation modes. For this latter branch, we thoroughly investigate the intermediate regime between two-stream and filamentation instabilities for arbitrary wave vectors. When some plasma temperature is allowed for, the system exhibits a critical angle at which waves are unstable for every k . Besides, in the relativistic regime, the most unstable mode on this branch is reached for an oblique wave vector. This study is especially relevant to the fast ignition scenario as its generality could help clarify some confusing linear issues of present concern. This is a prerequisite towards more sophisticated nonlinear treatments.

Slow Z-mode radiation from sounder-accelerated electrons

Quasi-electrostatic Z-mode waves created by the transmitting part of the OEDIPUS-C payload were measured on the receiving part at 1200 m distance. Solutions of the complete electromagnetic dispersion relation for a hot magnetoplasma reveal, however, that there is no solution that provides direct ray paths along the transmitter-receiver separation direction with the observed signal group delays. An interpretive model is therefore proposed in which sounder-accelerated electrons (SAE) radiate incoherently as they spiral along the magnetic field direction in the general direction of the receiving subpayload. Test-particle theory combined with the hot-plasma dispersion solution is used to predict the total electric field for previously reported SAE flux levels. It is found that voltage levels measured on the receiving dipoles have about the same order of magnitude as the predicted ones.

Testing Lorentz Invariance with GRB 021206

Since the discovery of the cosmological origin of gamma-ray bursts (GRBs), there has been growing interest in using these transient events to probe the quantum gravity energy scale in the range 1016-1019 GeV, up to the Planck mass scale. This energy scale can manifest itself through a measurable modification in the electromagnetic radiation dispersion relation for high-energy photons originating from cosmological distances. We have used data from the GRB of 2002 December 6 (GRB 021206) to place an upper bound on the energy dispersion of the speed of light. The limit on the first-order quantum gravity effects derived from this single GRB indicates that the energy scale is in excess of 1.8 × 1017 GeV. We discuss a program to further constrain the energy scale by systematically studying such GRBs.

On a nonlinear state of the electromagnetic ion/ion cyclotron instability

Abstract. We have investigated the nonlinear properties of the electromagnetic ion/ion cyclotron instability (EMIIC) by means of hybrid simulations (macroparticle ions, massless electron fluid). The instability is driven by the relative (super-Alfvénic) streaming of two field-aligned ion beams in a low beta plasma (ion thermal pressure to magnetic field pressure) and may be of importance in the plasma sheet boundary layer. As shown in previously reported simulations the waves propagate obliquely to the magnetic field and heat the ions in the perpendicular direction as the relative beam velocity decreases. By running the simulation to large times it can be shown that the large temperature anisotropy leads to the ion cyclotron instability (IC) with parallel propagating Alfvén ion cyclotron waves. This is confirmed by numerically solving the electromagnetic dispersion relation. An application of this property to the plasma sheet boundary layer is discussed.

Electrostatic surface waves in a dusty plasma

Electromagnetic dispersion relation of a surface wave is obtained propagating on an interface between a vacuum and a dusty plasma, which consists of electrons and ions on their respective Boltzmann distributions and cold dust particles providing the inertia of the plasma and carrying a certain portion of the negative charge of the plasma. The electrostatic spectrum is interesting, since the branch of the high frequency electron wave is of an acoustic type whose frequency range is confined to 0.5⩽ω/ωpe<1 (ωpe is the electron plasma frequency). The low frequency ion surface wave resembles the volume dust acoustic wave and may be called a dust acoustic surface wave.

Nonrelativistic electromagnetic surface waves: dispersion properties in a magnetized dusty electron-positron plasma

Nonrelativistic electromagnetic surface waves propagating on the plane interface between dusty electron-positron plasma and vacuum are investigated by specular reflection procedure. In the presence of an applied magnetic field (B(0)=B(0)yinsertion mark) directed perpendicular to both the interface normal and the wave vector, transverse electromagnetic modes are studied in terms of the dispersion relation. The analytic modes are derived and discussed with the aid of some numerical analysis. The cold electromagnetic surface wave dispersion relation considering the effect of dust particle shows that possible modes appear only when the normalized frequency (omega;) and the wave vector (&Kmacr;) satisfy the condition Omega;<omega;<Omega;+(1+delta)/2 and &Kmacr;>Omega;, where delta(=n(0-)/n(0+)) is the parameter of charge imbalance in the plasma and Omega; is the normalized cyclotron frequency.

Electromagnetic surface wave modes in nonrelativistic electron–positron plasmas

Electromagnetic surface waves propagating on the plane interface (x=0) between the electron–positron plasma and vacuum are investigated by the specular reflection procedure. The transverse electromagnetic modes are studied in terms of dispersion relation both in the presence and absence of an applied magnetic field. The analytic modes for some limiting cases are derived and discussed with the aid of some numerical analysis. In the presence of an applied magnetic field (B0=B0ŷ) directed perpendicular both to the interface normal and the wave vector, the cold electromagnetic surface wave dispersion relation shows that possible modes appear only when the frequency (ω) and the wave vector (k) satisfy the condition Ω2&amp;lt;ω2&amp;lt;Ω2+ωp2 and c2k2&amp;gt;Ω2 (Ω is cyclotron frequency).

THE STATIC MAGNETIC MODE AND THE OSCILLATING ELECTRIC FIELD IN THE INTERACTION OF ELECTRO MAGNETIC FIELD WITH IONIZATION FRONT

Using the electromagnetic dispersion relation in the cold plasma, we research the static magnetic mode that arises in the process of interaction of electromagnetic wave with moving- ionization front driven by an intense laser and find that an oscillating electric field is excited- under a special condition. We also define the condition under which the oscillating electric field appears.

Kinetic theory mode properties: Application to low frequency waves in the ion foreshock

The majority of previous works studying ULF waves in the Earth's ion foreshock have been based only on the magnetic field fluctuations and most of them have based their mode identification on fluid models. To provide a more complete description of the waves, it is necessary to consider the fluctuations of the particle population and to use the values of wave identifiers derived from a kinetic model. We use the electromagnetic dispersion relation derived from linear Vlasov theory to evaluate various plasma-field correlations for the hot beam right-hand and left-hand resonant instabilities under conditions consistent with the foreshock. Comparison of the observed Alfvén ratio, parallel compressiblity, cross-helicity, magnetic compression and polarization for the waves observed in 10 intervals by AMPTE-UKS with the theoretical values, allows us to identify regions with Alfvénic waves and regions with magnetosonic fluctuations.

Properties of ultra low frequency upstream waves at Venus and Saturn: A comparison

The upstream regions of all planets, except Pluto, have been investigated, using in situ spacecraft measurements and a variety of analysis techniques. The detailed studies at Earth indicate that these waves are generated locally in the magnetically connected solar wind by the interaction with ions backstreaming from the shock. However, since the properties of the solar wind vary with heliocentric distance and since properties of planetary shocks depend on plasma beta, interplanetary magnetic field (IMF) spiral angle and Mach number, the amount of heating, acceleration efficiencies, etc. significantly change with heliocentric distance. In turn the waves seen at each planet propagate not in the same but different (physical) propagation modes. In this paper we compare the ULF wave observations at an outer and an inner planet. We use the results of the ratio, quantites easily derivable with sufficient accuracy at each planet. We use the full electromagnetic dispersion relation for comparison with theoretical predictions.

Standard and nonstandard plasma neutrino emission revisited

view Abstract Citations (185) References (22) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Standard and Nonstandard Plasma Neutrino Emission Revisited Haft, Martin ; Raffelt, Georg ; Weiss, Achim Abstract On the basis of Braaten and Segel's representation of the electromagnetic dispersion relations in a QED plasma we check the numerical accuracy of several published analytic approximations to the plasma neutrino emission rates. As we find none of them satisfactory we derive a new analytic approximation which is accurate to within 4\%\ where the plasma process dominates. The correct emission rates in the parameter regime relevant for the red giant branch in globular clusters are larger by about $10-20$\% than those of previous stellar evolution calculations. Therefore, the core mass of red giants at the He flash is larger by about $0.005\M_\odot$ or 1\% than previously thought. Our bounds on neutrino magnetic dipole moments remain virtually unchanged. Publication: The Astrophysical Journal Pub Date: April 1994 DOI: 10.1086/173978 arXiv: arXiv:astro-ph/9309014 Bibcode: 1994ApJ...425..222H Keywords: Computational Astrophysics; Emission Spectra; Magnetic Dispersion; Neutrinos; Numerical Analysis; Plasmas (Physics); Quantum Electrodynamics; Approximation; Magnetic Dipoles; Stellar Cores; Stellar Evolution; Astrophysics; ELEMENTARY PARTICLES; PLASMAS; RADIATION MECHANISMS: MISCELLANEOUS; STARS: GIANTS; STARS: INTERIORS; Astrophysics E-Print: LaTeX, 16 pages, 12 figures on request from authors, MPI-Ph/93-65 full text sources arXiv | ADS | Related Materials (1) Erratum: 1995ApJ...438.1017H

Growing “Alfvenic” modes in the upstream region of Saturn

Recent studies of low‐frequency electromagnetic waves upstream of the Saturn bow shock have shown that these waves, in contrast to those at Earth, are observed not in one, but in at least two, distinct frequency bands. The results of wave mode identification based on the Hall‐MHD model of plasma and observed wave polarization suggested that these waves propagate in the high beta intermediate mode. However, the underlying instability was not unambiguously determined. In the present paper we use the full electromagnetic dispersion relation derived from linear Vlasov theory in order to examine which of the plasma modes, with observed properties, are unstable in an isotropic Maxwellian plasma in the presence of backstreaming proton beams consistent with Voyager 2 observations at Saturn. As a result we find that the unstable “Alfvenic” beam mode, as well as resonant and non‐resonant fast magnetosonic modes have properties consistent with the data. Moreover, we find that in contrast to the Earth' upstream waves, at Saturn no “kinetic” normal mode can account for the observed magnetic polarization.

On the dispersion relations for parametric instabilities of parallel‐propagating Alfvén waves

We consider the dispersion relation for the parametric instabilities of large‐amplitude, circularly polarized Alfvén waves, propagating parallel to the ambient magnetic field. A linear perturbation analysis is employed, and the perturbations are taken to propagate along the ambient field. The standard analysis which has been used previously assumes that density perturbations vary as exp [i(kz ‐ ωt)]; this defines the meaning of ω and k. However, the differential equations have periodic coefficients, implying that Floquet analysis should be used. We here present an analysis based on Floquet's theorem. The result is a hierarchy of dispersion relations. However, all the dispersion relations are found to be equivalent to the one obtained via the standard analysis; the differences between them are due only to how ω and k are defined. Thus we conclude that physically there is really only one dispersion relation, namely the “electrostatic dispersion relation,” which is in agreement with earlier works. However, we disagree with Viñas and Goldstein (1991b), who obtained additional dispersion relations which they have called the “electromagnetic dispersion relations.” Their additional dispersion relations are a consequence of first truncating the dispersion relation for obliquely propagating perturbations and then taking the limit of parallel‐propagating perturbations.

Electromagnetic semi-local kinetic analysis of the electron temperature gradient mode in tokamaks

Electromagnetic (finite beta) effects on the toroidal electron temperature gradient mode have been investigated in terms of an electromagnetic semi-local kinetic dispersion relation. For this mode, finite beta is destabilizing, in contrast to the ion temperature gradient mode. However, a relatively steep temperature gradient, ϵT = LT/R < 0.15, is required for the instability. The most unstable mode satisfies ω ≃ ωTe (the electron transit mode).

Novel method for determining the electromagnetic dispersion relation of periodic slow wave structures

A novel method for calculating the dispersion relation of electromagnetic modes in an arbitrary periodic slow wave structure is reported. In this method it is sufficient to know the frequencies corresponding to three special wave number values, with other points calculated using an approximate analytical expression. This technique was successfully applied to determine the dispersion relation of the TM01 mode in a sinusoidally corrugated slow wave structure. This structure is commonly used in relativistic high-power backward wave oscillators and traveling-wave tubes, and is expected to have many additional applications.

Coupling of phonon-polariton modes at dielectric-dielectric interfaces by the ATR technique

We report the calculated ATR dispersion relation of the interface phonon-polariton modes in the prism-dielectric-dielectric configuration. Comparison of electromagnetic dispersion relations (EMDR) with the ATR dispersion relations are presented for three different interfaces: I) GaAs/GaP, II) CdF2/CaF2 and III) CaF2/GaP in two propagation windows, using the Otto and Kretschmann geometries for p-polarized light. We have studied the three cases using angle and frequency scans for each window and geometry. The results indicate that it is possible to excite and detect phonon-polariton modes at the dielectric-dielectric interface.

Ray Tracing Analyses of Lower Hybrid Waves in Heliotron/Torsatron

Lower hybrid (LH) wave propagation and absorption caused by ion Landau damping and electron Landau damping in the heliotron/torsatron were studied for ion heating, electron heating and current drive. The analyses are based on the ray tracing method using the electromagnetic plasma dispersion relation, including warm plasma effects. In the heliotron/torsatron, the magnetic field has large ripples along the magnetic field line produced by external helical coils. This property changes the cross-sectional shape of the LH resonance layer from a circular shape in tokamaks. The refractive indices N ⊥ and N // , perpendicular and parallel to the magnetic field line, respectively, also change in oscillation along the ray trajectory. LH waves are absorbed at the places where the refractive index is large or at the high-field side near the helical coils.