Excitation Of Electron Plasma Wave Research Articles

Nonlinear Interaction of a Right-Handed Circularly Polarized Gaussian Electromagnetic Beam with an Electron-Plasma Wave: Generation of Ion-Acoustic Wave

This paper presents an investigation of the nonlinear interaction of a high-power right-handed circularly polarized Gaussian electromagnetic beam with an electron-plasma wave in a hot collisionless magnetoplasma. Because of the nonuniform intensity distribution of the electromagnetic beam, in a plane transverse to the direction of propagation, the ponderomotive force becomes finite and leads to the modification in the background carrier density. This leads to the nonlinear coupling between the electromagnetic beam and the electron-plasma wave. Consequently, the focusing of the electron-plasma wave may take place, leading to the enhancement in its amplitude. The excited electron-plasma wave may again interact with the electromagnetic beam and generate an ion-acoustic wave of appreciable power. The power of the generated ion-acoustic wave increases as we approach the critical density region.

Numerical estimation of SPS microwave impact on ionospheric environment

A possible interaction with the ionosphere of an intense microwave which will be used in energy transmission from Solar Power Satellite (SPS) to the Earth, is numerically studied. Microwave heating of the ionosphere and nonlinear excitation of electron plasma waves and ion acoustic waves are numerically studied for a model ionosphere.

Remote Excitation of Electron Plasma Waves by a Modulated Laser Beam

Remote Excitation of Electron Plasma Waves by a Modulated Laser Beam

Nonlinear Effects in Collective Absorption

The collective absorption of high intensity laser radiation is analyzed numerically. Density profile modification due to the ponderomotive force associating laser radiation and the excited electron plasma waves is self-consistently taken into account, and the intensity dependences of the absorption efficiency are obtained. In the high intensity regime, the absorption efficiency is found to be strongly enhanced in the plasma without flow, but reduced with supersonic flow.

Nonlinear interaction of an intense laser beam with an electron plasma wave: generation of ion-acoustic wave

Presents an investigation of the nonlinear interaction of a high power Gaussian laser beam with the excited (by the laser) electron plasma wave in a hot collisionless unmagnetised plasma. On account of the interaction between the two waves the ponderomotive force at the difference frequency becomes finite and may lead to the generation of another electrostatic wave in the plasma. It has beem shown that, when the frequency of the laser beam is in the vicinity of the electron plasma frequency, the generated electrostatic wave is a low frequency ion wave. For a typical laser plasma and CO2 laser the maximum power associated with the ion wave is found to be approximately 70 ergs s-1.

Dynamic interaction of intense microwaves with plasma

The ponderomotive force of the parametrically excited electron plasma waves drastically modifies the density profile. The asymptotic density profile has a subcritical density plateau followed by a density jump to supercritical densities which reduces the parametric instabilities, as observed in particle simulation calculations.

Thin sheets of energetic electrons upstream from the Earth’s bow shock

ISEE spacecraft observations show that energetic, ≥ 16 keV electrons are injected into the region upstream from the Earth’s bow shock in a thin sheet which lies just behind the sheet of interplanetary magnetic field lines that are tangent to the shock surface. Lower energy electrons leave the shock over a much broader region. Although the energetic electron intensity varies, the sheet is nearly always present and may be a quasi‐steady state feature of the bow shock. The electron velocity distribution in the thin sheet is strongly peaked and is responsible for excitation of electron plasma waves.

Sum-frequency excitation of electron plasma waves

Nonlinear mixing of two circularly polarized electromagnetic waves propagating in a plasma along a uniform static magnetic field is considered. Resonant excitation of electron plasma waves is found to be possible at the difference frequency if the incident waves are both extraordinary or both ordinary and at the sum frequency if one incident wave is extraordinary and the other is ordinary. Formulas for the absorption efficiency due to sum-frequency excitation are derived and the results of a numerical study are presented.

Magnetic field effects on the beat heating of a plasma

The excitation of electron plasma waves by interaction of two opposed electromagnetic waves in a magnetized plasma is examined. A beat frequency wave may be resonantly generated as either of two natural modes which have frequencies small compared to the sum frequency of the source waves. An analysis is based on Maxwell's equations and the electron-gas moment equations with the pressure tensor neglected. A formula is derived for the power absorbed per unit volume of plasma in a uniform, static magnetic field. The effects of the magnitude and direction of the magnetic field on the plasma heating rate are studied numerically.

Transverse flux constraint for excitation of electron plasma waves in a magnetic field

The analog of the conservation law for photon number is derived for a three-wave interaction involving two circularly polarized electromagnetic waves and an electron plasma wave propagating along a uniform static magnetic field.

Higher harmonics of electron plasma waves

A model based on nonlinear mixing of dispersive waves is used to predict higher harmonic waves generated by weakly nonlinear electron plasma waves. The total harmonic wave is given by superposition of modes which lie at different points (with the same frequency) in the dispersion diagram. The model well explains the experimental results concerning the harmonic waves produced by externally excited electron plasma waves propagating along a collisionless plasma column.

Temperature effects on the nonlinear absorption of radiation by optical mixing in a plasma

An analysis of the heating of plasma with arbitrary temperature and density inhomogeneity by parallel or antiparallel laser beams is presented. The average power density absorbed by a warm plasma due to the excitation of electron plasma waves at the beat frequency is determined as a function of the frequency mismatch. Formulas for the absorption efficiency of a plasma with both temperature and density variation along the beams are derived. Linear and parabolic temperature distributions are considered explicitly.

Delayed emission excited by a high power microwave pulse

An experiment is performed to study the interaction of a high power microwave pulse with a magnetized dense plasma. A delayed emission appears after the complete termination of a pumping microwave pulse when the frequency of the pumping wave is equal to the harmonics of the cyclotron frequency and is near the plasma frequency. Two types of delayed emission (types I, II) are observed, depending on the experimental conditions. The type I delayed emission is characterized by the frequency spectrum with sharp peaks at cyclotron harmonics (mfce:m=1,2...), type II with broad peaks between (m+1/2) fce and (m+1) fce. The main properties of these phenomena are explained in terms of anomalous power absorption at cyclotron harmonic resonances and excitation of electron plasma waves by an anisotropic electron velocity distribution. Each type of delayed emission can be triggered artificially by a sudden decrease in cold background plasma density and is suppressed by an increase in cold plasma.

Delayed Emission Excited by a High Power Microwave Pulse

An experiment is performed to study the interaction of a high power microwave pulse with a magnetized dense plasma. A delayed emission appears after the complete termination of a pumping microwave pulse when the frequency of the pumping wave is equal to the harmonics of the cyclotron frequency and is near the plasma frequency. Three types of the delayed mission (type I, II, III) are observed, depending on the experimental conditions. Type I delayed emission is characterized by the frequency spectrum with sharp peaks at cyclotron harmonics (mfce m= 1, 2, ..), type II with broad peaks between (m+1/2) fce and (m + 1) fce and type III with broad peak between 0.8 fce and fce. Main properties of these phenomena are explained in terms of anomalous power absorption at cyclotron harmonic resonances and excitation of electron plasma waves by an anisotropic electron velocity distribution. Each type of the delayed emission can be triggered artificially by a sudden decrease of cold back ground plasma density and is suppressed by an increase of cold plasma. It can be also triggered by a pulsed electron beam.

Criteria for plasma-wave losses for electrons streaming from an acceleration region

view Abstract Citations (12) References (9) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Criteria for plasma-wave losses for electrons streaming from an acceleration region. Smith, D. F. Abstract Consistent criteria are derived for determining when losses due to collective excitation of electron plasma waves will be important for electrons streaming from an acceleration region. The analysis is nonrelativistic and one-dimensional, but includes the effect of Coulomb collisions. These criteria are applied to source models for solar hard X-ray bursts, and it is shown that these losses will almost never be important for the observations obtained thus far. The case in which the acceleration region and the X-ray source partially overlap is considered briefly. Publication: The Astrophysical Journal Pub Date: October 1975 DOI: 10.1086/153914 Bibcode: 1975ApJ...201..521S Keywords: Astronomical Models; Electron Plasma; Particle Acceleration; Plasma Waves; Solar X-Rays; Bursts; Collisional Plasmas; Criteria; Energy Dissipation; Nonrelativistic Mechanics; Plasma-Particle Interactions; Solar Physics full text sources ADS |

Mechanisms for Flash Phase Phenomena in Solar Flares

Mechanisms for explaining the various forms of particles and radiation observed during the flash phase of solar flares are reviewed under the working hypothesis that the flash phase is the time in which electrons and to a lesser degree protons are accelerated in less than one second. A succession of such accelerations is allowed to explain longer lasting or quasi-periodic phenomena. Mechanisms capable of such acceleration are reviewed and it is concluded that first-order Fermi acceleration in a reconnecting current sheet is the most likely basic process. Such acceleration, however, gives rise to a rather narrow distribution of particle velocities along a given field line which is unstable to the production of electron plasma and ion-acoustic waves. This plasma turbulence can heat the plasma to produce soft X-rays and filter the initially narrow velocity distribution to produce a power law energy distribution. Electrons travelling inward from the acceleration region produce hard X-rays by bremsstrahlung and microwave bursts by gyro-synchrotron emission. Whereas the interpretation of X-ray spectra is relatively straightforward, the interpretation of microwave spectra is difficult because the source at low frequencies can be made optically thick by several different mechanisms.Electrons travelling further inward presumably thermalize and produce impulsive EUV and Hα emission. The theory for these emissions, although amenable to present techniques in radiative transfer, has not been worked out. Electrons travelling outward give rise to type III radio bursts by excitation of electron plasma waves and the electrons observed at the Earth. Study of the interaction of a stream of electrons with the ambient plasma shows that the electron spectra observed at the Earth do not necessarily reflect their spectrum at the acceleration region since they interact via plasma waves as well as through Coulomb collisions. The mechanisms for the conversion of plasma waves into radiation and the propagation of the radiation from its source to the observer are reviewed.

Emission of electron cyclotron harmonics from a non-Maxwellian plasma

Microwave emission of electron cyclotron harmonics from a plasma of a reflex discharge (PIG) was investigated. It was shown that besides the well known phenomenon of emission of electron cyclotron harmonics with a comparatively low intensity (radiation temperature TR approximately 10/100 eV) and broad emission lines ( Delta omega / omega =(2/3).10-2) Landauer (1961), a new type of emission took place. This emission has extremely high intensity (TR approximately 108 eV), narrow emission lines ( Delta omega / omega =(1/3).10-3) and is emanated in a form of short pulses ( tau approximately=1/5 mu sec). Main properties of this phenomenon are explained in terms of excitation of electron plasma waves by a group of nonequilibrium electrons with isotropic velocity distribution.

Excitation of Electron-Plasma Waves by the Interaction of an Ion Beam with a Plasma

Excitation of Electron-Plasma Waves by the Interaction of an Ion Beam with a Plasma