Effect Of Parallel Electric Field Research Articles

Effect of parallel electric field on the linear stability between a Newtonian and a power-law fluid in a microchannel

Effect of parallel electric field on the linear stability between a Newtonian and a power-law fluid in a microchannel

Effect of parallel electric field on electromagnetic ion-cyclotron waves with hot anisotropic plasma

The effect of parallel electric field on the growth rate, parallel and perpendicular resonant energy of the electromagnetic ion-cyclotron (EMIC) waves with general loss-cone distribution function in hot anisotropic plasma in auroral acceleration region is investigated by particle aspect approach. The ion beam driven by parallel electric field is included in the analysis whereas electrons are assumed mixed with the back ground plasma. Plasma consisting of resonant and non-resonant particles has been considered. It is assumed that the resonant particle and ion beam participate in energy exchange with the wave, whereas non-resonant particles support the oscillatory motion of the wave. We observed that the parallel electric field is to control the growth rate of the EMIC wave, whereas the effect of steep loss-cone distribution is to enhance the growth rate and perpendicular heating of the ions. This study is relevant to analyse the broad scenario of EMIC waves in the auroral acceleration region of the earth’s magnetoplasma.

Kinetic Alfven wave in the presence of parallel electric field with general loss-cone distribution function: A kinetic approach

In past, kinetic Alfven waves are widely investigated regarding the transfer of energy from the magnetosphere to the ionosphere. These waves are supposed to be responsible for the acceleration of auroral electrons to exhibit auroral phenomena. The existence of parallel electric fields is always reported in association with the kinetic Alfven waves. In the present investigation, assuming parallel electric fields developed by different mechanism, the dispersion relation and growth/damping rate of the kinetic Alfven Wave (KAW) in the presence of parallel electric field are evaluated with general loss-cone distribution using the kinetic approach. The wave frequency w and growth/damping rate gL are obtained for two regimes of propagation k^ri 1, where k^ is perpendicular wave number andri is the ion-gyro radius. The results of the present study show that the frequency w and growth/damping rate of wave depend upon the distribution indices, parallel electric field and k^ri. The generation of kinetic Alfven wave by the combined effect of parallel electric field and loss-cone distribution indices (J), at a particular range of k^ri is noticed. Thus the propagation of kinetic Alfven wave and loss of the Poynting flux from plasma sheet boundary layer (PSBL) to the ionosphere can be explained more effectively on the basis of present investigation. The results of the present study show that the parallel electric field in the presence of loss-cone distribution index is an important parameter to study KAW in the PSBL. The finding of the present investigation is to report that auroral phenomena are suitably described by kinetic Alfven wave in the presence of parallel electric field and the general loss-cone distribution function. Key words: Kinetic Alfven wave, Plasma-sheet-boundary-layer, Parallel electric field, Kinetic theory, Loss-cone distribution function.

Study of kinetic Alfven wave (KAW) in plasma – sheet-boundary- layer

The effect of parallel electric field with general loss-cone distribution function on the dispersion relation and damping rate/growth rate of the kinetic Alfven wave (KAW) is evaluated by kinetic approach. The generation of KAW by the combined effect of parallel electric field and loss-cone distribution indices (J) at a particular range of k⊥ρi (k⊥ρi <1 and k⊥ρi >1) is noticed, where k⊥ is perpendicular wave number and ρi is the ion-gyro radius. Thus the propagation of KAW and loss of the Poynting flux from plasma sheet boundary layer (PSBL) to the ionosphere can be explained on the basis of present investigation. It is found that the present study also shows that the loss-cone distribution index is an important parameter to study KAW in the PSBL.

Erratum: “The effect of parallel electric field in shock waves on the acceleration of relativistic ions, electrons, and positrons” [Phys. Plasmas 16, 112308 (2009)

Erratum: “The effect of parallel electric field in shock waves on the acceleration of relativistic ions, electrons, and positrons” [Phys. Plasmas 16, 112308 (2009)

The effect of parallel electric field in shock waves on the acceleration of relativistic ions, electrons, and positrons

The effect of an electric field E∥ parallel to the magnetic field B on particle acceleration in shock waves is studied. With test particle calculations, for which the electromagnetic fields of shock waves are obtained from one-dimensional, fully kinetic, electromagnetic, particle simulations, the motions of relativistic ions, electrons, and positrons are analyzed. In these simulations, the shock speed vsh is taken to be close to c cos θ, where θ is the angle between the external magnetic field and wave normal, and thus strong particle acceleration takes place. Test particle motions calculated in two different methods are compared: In the first method the total electric field E is used in the equation of motion, while in the second method E∥ is omitted. The comparison confirms that in the acceleration of relativistic ions E∥ is unimportant for high-energy particles. For the acceleration of electrons and positrons, however, E∥ is essential.

Electron heating and airglow emission due to lightning effects on the ionosphere

This study is the first attempt to consider lightning effects on the F2 region. Although pulsed electric fields parallel to the geomagnetic field have been observed by every rocket flight over active thunderstorms at thermospheric heights, their existence remains controversial. Predicting the disturbance of ionospheric parameters induced by these electric fields may lead to verifying them using ground‐based ionospheric observations. This study is also important for understanding the kinetics of ionospheric plasma disturbed by pulsed parallel electric fields. These fields can accelerate electrons from pulse to pulse. If the pause between flashes is longer than τen, electrons are scattered by elastic collisions with neutrals and transformed into thermal electrons with a corresponding electron temperature enhancement. Inelastic collisions of electrons with neutrals will become more important with increased energy and, subsequently, the electron energy distribution (EED) can differ from a Maxwellian distribution. The vibrational excitation of N2 is extremely important as a source of inelastic collisions for energy ≥2 eV. This vibrational barrier can influence the EED. An electron kinetics model induced by pulsed parallel electric fields in ionospheric plasma is developed here. The accelerated and heated electrons can excite airglow in the F2 region. Excitation of red line emissions is most effective. Red line intensities during thunderstorms are predicted to be much higher than the background intensity. Our model also predicts a significant increase in electron temperature in the F2 region during a strong thunderstorm. Opportunities for observing the ionospheric effects of parallel electric fields induced by lightning are discussed.

Effect of parallel electric field on Alfven wave in thermal magnetoplasma

Dispersion relation, dissipation and growth of Alfven wave in the presence of parallel electric field and electron thermal velocity have been obtained by investigating the trajectories of the charged particles. The effect of parallel electric field is included with the zeroth-order distribution function through modification of the electron thermal velocity parallel to ambient magnetic field. It is found that the parallel electric field and thermal velocity of the electrons enhance the damping/growth rate of the wave according to the direction of electric field. The applicability of theory to explain auroral acceleration in the space plasma has been discussed.

Electromagnetic ion-cyclotron instability in the presence of a parallel electric field with general loss-cone distribution function - particle aspect analysis

Abstract. The effect of parallel electric field on the growth rate, parallel and perpendicular resonant energy and marginal stability of the electromagnetic ion-cyclotron (EMIC) wave with general loss-cone distribution function in a low β homogeneous plasma is investigated by particle aspect approach. The effect of the steepness of the loss-cone distribution is investigated on the electromagnetic ion-cyclotron wave. The whole plasma is considered to consist of resonant and non-resonant particles. It is assumed that resonant particles participate in the energy exchange with the wave, whereas non-resonant particles support the oscillatory motion of the wave. The wave is assumed to propagate parallel to the static magnetic field. The effect of the parallel electric field with the general distribution function is to control the growth rate of the EMIC waves, whereas the effect of steep loss-cone distribution is to enhance the growth rate and perpendicular heating of the ions. This study is relevant to the analysis of ion conics in the presence of an EMIC wave in the auroral acceleration region of the Earth's magnetoplasma.

Effect of parallel electric field on electrostatic ion-cyclotron instability in anisotropic plasma in the presence of ion beam and general distribution function—Particle aspect analysis

Dispersion relation, resonant energy transferred, growth rate and marginal instability criteria for the electrostatic ion-cyclotron wave with general loss-cone distribution in low- β anisotropic, homogeneous plasma in the auroral acceleration region are discussed by investigating the trajectories of the charged particles. Effects of the parallel electric field, ion beam velocity, steepness of the loss-cone distribution and temperature anisotropy on resonant energy transferred and growth rate of the instability are discussed. It is found that the effect of the parallel electric field is to stabilize the wave and enhance the transverse acceleration of ions whereas the effect of steepness of loss-cone, ion beam velocity and the temperature anisotropy is to enhance the growth rate and decrease the transverse acceleration of ions. The steepness of the loss-cone also introduces a peak in the growth rate which shifts towards the lower side of the perpendicular wave number with the increasing steepness of the loss-cone.

Determination of the electron cyclotron current drive profile

Evaluation of the profile of non-inductive current density driven by absorption of electron cyclotron waves (ECCD) using time evolution of the poloidal flux indicated a broader profile than predicted by theory. To determine the nature of this broadening, a 1-1/2 D transport calculation of current density evolution was used to generate the signals which the DIII-D motional Stark effect (MSE) diagnostic would measure in the event that the current density evolution followed the neoclassical Ohm's law with the theoretical ECCD profile. Comparison of the measured MSE data with the simulations indicates the experimental data is consistent with the narrow ECCD profile predicted by theory. The simulations indicate the magnitude of the ECCD is at or above the value found in Fokker–Planck calculations of the ECCD, which includes quasilinear and parallel electric field effects.

The effect of parallel electric fields on the orientation of polycrystalline zinc oxide thin films produced by reactive evaporation and oxidation of zinc

The effect of an electric field (detached electrodes) on the crystal orientation of zinc oxide thin film was investigated. Two methods, direct and indirect, were utilized to produce zinc oxide thin films. In the direct method (reactive evaporation) oxygen was introduced into the zinc vapour stream and ZnO films were deposited on cold substrates in a vacuum system. Parallel electric fields were applied during the reaction process. It was observed that the electric field had no effect on the preferred c-axis orientation of the ZnO crystals. There was no significant difference in the crystal size or surface texture of ZnO samples subjected to electric fields with respect to the sample that experienced no electric field. In the indirect method (oxidation) electric fields were applied during the evaporation of zinc then the samples were oxidized in air in a furnace at 600 ‡C. Here the application of electric field improved the c-axis orientations. The crystal size remained unchanged, but the surface morphology was affected by the application of the electric field. Whenever the c-axis orientation improved, crystals on the surface became rounded and a more ordered microstructure was observed.

Overview of Alfven eigenmode experiments in JET

Results from the first experiments to drive Alfven eigenmodes (AEs) with antennas external to a tokamak plasma are presented. In ohmically heated plasma discharges, direct experimental measurements of the damping of toroidicity induced AEs (TAEs) have allowed an identification of different regimes corresponding to different dominant TAE absorption mechanisms with a wide range of damping rates, 10-3 ⩽ γ/w ⩽ 10-1. In plasmas heated by ion cyclotron resonance heating, neutral beam injection heating, lower hybrid heating and high plasma current ohmic heating, a new class of weakly damped Alfven eigenmodes, the kinetic Alfven eigenmodes, predicted in theoretical models that include finite Larmor radius and finite parallel electric field effects, has been identified experimentally

Two-fluid equations for singular modes with frequency comparable to the parallel ion acoustic frequency

Braginskii’s two-fluid equations, with collisional effects neglected and electron fluid assumed to be isothermal along the magnetic field lines, are employed to obtain the singular mode equations. While the ordering analysis in the paper indicates that, in the intermediate frequency regime (i.e., that with the frequency of the modes higher than the ion acoustic frequency along the magnetic field lines, but lower than the electron one), the stabilizing finite Larmor radius (FLR) effect on the modes dominates over other collisionless, two-fluid effects, the paper is devoted to the investigation of the comparable frequency regime (i.e., that with the frequency of the modes comparable to the ion acoustic frequency along the field lines). It is found that, in such a regime, the parallel electric field is excited and the plasma behaves nonadiabatically. The singular mode equations consist of two coupled second-order partial differential equations, in which the FLR, the plasma compression, and the parallel electric field effects are present. The results are discussed, and a comparison with the ideal magnetohydrodynamic formalism is given.

Effect of parallel electric fields on the propagation paths of auroral kilometric radiation

The effect of parallel electric fields on the angular distribution of auroral kilometric radiation at frequencies between 56.2 and 500 kHz is examined by ray tracing computations in polar wind and auroral plasma cavity models. The results show that the effect is not significant at frequencies between 100 and 500 kHz in both models. The presence of an electric field does affect the angular distribution at 56.2 kHz where the ray paths representing the boundary of the emission cone in the dayside and nightside sectors of the noon‐midnight meridian are tilted equatorward and poleward, respectively, by about 20° (i.e., the cone axis is redirected toward the evening sector by about 20°). An attempt to match the results with the observations shows that the initial wave normal angles for these ray paths are 262° and 85.5°, respectively. The ray paths computed in the plasma cavity model also yield the same result except for some minor adjustment with the initial wave normal angles.

Alpha-Alfvén local dispersion relation and solutions

The local dispersion relation for shear and kinetic Alfvén waves is derived for arbitrary alpha particle distribution functions and analyzed for a set of representative distribution functions. Including both the velocity dependence of magnetic drift and temperature gradients is found to have the most striking effect on the partial growth rate associated with alpha particles for shear Alfvén waves. Parallel electric field effects are included and found to make significant changes in the damping associated with electrons and ions. The formalism parallels that used in reduced magnetohydrodynamics, so that it can be readily extended to calculations incorporating more detailed and realistic equilibrium geometry.

Effect of parallel electric fields on whistler mode waves in an anisotropic Jovian magnetospheric plasma

The effect of parallel electrostatic field on the amplification of whistler mode waves in an anisotropic bi-Maxwellian weakly ionized plasma for Jovian magnetospheric conditions has been carried out. The growth rate for different Jovian magnetospheric plasma parameters forL = 5.6Rj has been computed with the help of general dispersion relation for the whistler mode electromagnetic wave of a drifted bi-Maxwellian distribution function. It is observed that the growth or damping of whistler mode waves in Jovian magnetosphere is possible when the wave vector is parallel or antiparallel to the static magnetic field and the effect of this field is more pronounced at low frequency wave spectrum.

A kinetic‐magnetohydrodynamic model for low‐frequency phenomena

A hybrid kinetic‐magnetohydrodynamic (MHD) model is presented for describing low‐frequency phenomena in high‐beta (β ∼ O(1)) anisotropic plasmas that consist of two components: a low‐energy core component and an energetic component with low density. The kinetic‐MHD model treats the low‐energy core component by magnetohydrodynamic description, the energetic component by a kinetic approach such as the gyrokinetic equation, and the coupling between the dynamics of these two components through plasma pressure in the momentum equation. The kinetic‐MHD model optimizes both the physics contents and the theoretical efforts in studying low‐frequency MHD waves and transport phenomena in general magnetic field geometries and can be easily modified to include the core plasma kinetic effects if necessary. It is applicable to any magnetized collisionless plasma system where the parallel electric field effects are negligibly small. In the linearized limit, two coupled eigenmode equations for describing the coupling between the transverse Alfvén type and the compressional Alfvén type waves are derived. The eigenmode equations are identical to those derived from the full gyrokinetic equation in the low‐frequency limit and were previously analyzed both analytically and numerically to obtain the eigenmode structure of the drift mirror instability (Cheng and Lin, 1987) which explains successfully the multisatellite observation of the antisymmetric field‐aligned structure of the compressional magnetic field of Pc 5 waves (Takahashi et al., 1987) in the magnetospheric ring current plasma. Finally, a quadratic form is derived to demonstrate the stability of the low‐frequency transverse and compressional Alfvén type instabilities in terms of the pressure anisotropy parameter τ the magnetic field curvature‐pressure gradient parameter αp as defined in equations (31) and (69), respectively. A procedure for determining the stability of a marginally stable MHD wave due to wave‐particle resonances is also presented.

Representations of currents and magnetic fields in anisotropic magnetohydrostatic plasma: 2. General theory and examples

We develop a general treatment of field‐aligned currents in quasi‐static adiabatic plasma. The formalism is an extension of an an earlier analysis (Heinemann, 1990) to include electric and gravitational fields. The assumption that the particle motions are adiabatic along the magnetic field leads to an expression for the total current density that is a generalization of expressions given by Grad (1964) and Vasyliunas (1970). The current density is a vector function of the gradients of the field line constants characterizing the plasma and the gradients of field line integrals of the partial derivatives of the parallel pressure with respect to the constants. The use of the expression as the current source in Ampere's law leads to an equation governing the equilibrium of the system of plasma and magnetic field. Examples based on bi‐Maxwellian distribution functions suggest that the effects of thermal anisotropy can be about as large as the currents due to isotropic plasma and that the effects of parallel electric fields are of the same order of magnitude.

Large-scale electric fields in post-flare loops

As the electrical conductivity along the magnetic field in solar atmosphere is large, parallel electric fields have been neglected in most investigations. We will first demonstrate their importance for post-flare loops, and then introduce a model for them which takes into account the effect of parallel electric fields. The electric field calculated from the model is consistent with the electric field observed by Foukal et al. (1983).