Absorption Of Waves In Plasma Research Articles

Cold plasma modes in the chiral Maxwell-Carroll-Field-Jackiw electrodynamics

In this work, we study the propagation and absorption of plasma waves in the chiral Maxwell-Carroll-Field-Jackiw (MCFJ) electrodynamics. The Maxwell equations are rewritten for a cold, uniform, and collisionless fluid plasma model, allowing us to determine the new refractive indices and propagating modes. The cases of propagation parallel and orthogonal to the magnetic field are examined considering a purely timelike CFJ background that plays the role of the magnetic conductivity chiral parameter. The collective electromagnetic modes are associated with four distinct refractive indices associated with right-circularly polarized and left-circularly polarized waves. For each index, the propagation and absorption zones are illustrated for some specific parameter values. In low-frequency regime, we have obtained modified helicons with right- and left-circularly polarizations. The optical behavior is investigated by means of the rotatory power (RP) and dichroism coefficient. The existence of a negative refraction zone enhances the rotatory power. It is also observed RP sign reversal, a feature of rotating plasmas.

Analysis of solar narrow band dm-spikes observed at 1420 and 2695 MHz

Using both linear and nonlinear methods, narrow band dm-spikes recorded at 1420 and 2695 MHz on June 6, 2000, July 8, 2000, July 12, 2000, July 20, 2000, and March 28, 2001 were analyzed. In particular their time profiles were studied statistically. The mean characteristic times of the ascending and of the decaying parts of their profiles are comparable, even if the dispersion of the values is very broad. For selected spikes at 1420 MHz a more precise fitting technique using exponential profiles was applied. While in the decaying part the exponential trend can be generally found, in the ascending part the exponential form can be confirmed only in few cases. The ascending and decaying phase of spikes presumably correspond to the source instability evolution and the plasma wave absorption. Furthermore, durations and polarization values of both 1420 and 2695 MHz spikes were determined and compared with the results in literature. All the analyzed spike events were located near the solar disk center. The polarization values and their trend in spike groups and the nearly constant duration suggest that the polarization originates at the source itself or near it. Selected time series of spikes were tested with respect to low-dimensional determinism and nonlinearity. We found that spikes recorded at fixed frequencies are not governed by a linear stochastic process, as the underlying physical system contains nonlinear signatures.

Two-dimensional (r,z) plasma wave absorption and Poynting flux simulations for helicon sources

A two-dimensional (r,z) computer code is utilized to examine wave propagation, collisionless Landau, and collisional heating mechanisms in a helicon source operation.

Nonlinear resonance of plasma waves in the thermal irregularities of ionospheric plasma

We study the effect of striction plasma density disturbances on the generation intensity of longitudional cold and plasma oscillations due to polarization of the magnetic field-aligned ionospheric plasma irregularities with δNo<0 by a powerful radio wave. It is assumed that the plasma density level inside the irregularity intersects the upper-hybrid resonance level, in the vicinity of which the cold oscillations excited directly by a powerful radio wave are transformed to shorter-wave plasma oscillations. We consider the short plasma wave limit to reduce the problem to a system of two coupled equations for the cold wave induction and plasma wave electric field. The first equation is supplemented by a local source equal to the integral of the plasma wave electric field in the resonance region. The second equation involves the cold wave induction at the resonance point and describes the electric field of interacting waves in the resonance vicinity. We use simplifications connected with the small absorption of plasma waves propagating inside the irregularity and weak radiation of these waves outside the irregularity. These conditions correspond to the generation of eigenmodes of plasma oscillations trapped in the irregularity. We have obtained a resonance-type nonlinear equation for the electric field intensity (or energy flux) of eigenmode plasma waves with allowance for striction disturbances of the plasma density profile in the resonance region. It is shown that the striction expulsion of plasma is responsible for the occurrence of coefficients describing the change in the intensity of excitation and radiation of plasma waves at the irregularity boundary. Such an expulsion leads to variations of the efficient generation band of plasma eigenmodes with the total phase increment of the wave in the irregularity. It also leads to a change in the phase shift of the plasma wave reflected from the resonance. These coefficients and the nonlinear phase shift are expressed in terms of real wave functions of the nonlinear Airy equation which describes the electric field of the excited waves in the resonance vicinity when the dissipation is absent.

Cross-Magnetic-Field Heat Conduction in Non-neutral Plasmas

This Letter discusses cross-magnetic-field collisional heat transport for a non-neutral plasma in the typical operating regime ${\ensuremath{\lambda}}_{D}\ensuremath{\gg}{r}_{c}$, where ${\ensuremath{\lambda}}_{D}$ is the Debye length and ${r}_{c}$ is the cyclotron radius. The dominant transport mechanism is the exchange of energy associated with velocity components parallel to the magnetic field. For a thermal gradient scale length ${L}_{T}\ensuremath{\gtrsim}100{\ensuremath{\lambda}}_{D}$, the energy exchange is dominated by interactions between particles separated by $O({\ensuremath{\lambda}}_{D})$ and yields a thermal diffusivity $\ensuremath{\chi}\ensuremath{\sim}{\ensuremath{\nu}}_{c}{\ensuremath{\lambda}}_{D}^{2}$, where ${\ensuremath{\nu}}_{c}\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}n\overline{v}{b}^{2}$ is the collision frequency. The diffusivity is even larger for larger ${L}_{T}$, where the energy exchange is dominated by the emission and absorption of plasma waves.

Excitation of short-wave oscillations in the ionospheric plasma by the field of a high-power radio wave with extraordinary polarization due to induced scattering by ions

We analyze excitation of electron-cyclotron or upper hybrid oscillations of the ionospheric plasma at a frequency that is close to the pump frequency as a result of induced scattering of a high-power radio wave with extraordinary polarization by ions. The excited oscillations have a small wavelength of the order of the Larmor electron radius, which allows them to propagate near and below the reflection level of an extraordinary radio wave. We found the instability increment and threshold field, which results from collisional absorption of plasma waves. It is shown that the threshold field is minimal near the reflection level of an extraordinary radio wave when the radio wave frequency f0 is between electron harmonics nfBe with n≥2. In an ionospheric F layer it is of the order of 1 W/m. Such fields are easily obtained in ionospheric heating experiments allowing for radio-wave field swelling in the reflection region. In the vicinity of electron harmonics fo≅nfBe, the threshold field is increasing. For fo<nfBe with fo≅nfBe the instability does not develop because of the absence of plasma oscillations with a frequency that is close to the pump frequency (the latter also refers to the case fo<2fBe). The expressions obtained are generalized to the case in which the instability under consideration is excited by the field of an ordinary radio wave in the region of its quasilongitudinal propagation. We discuss the possibility of using the emergence of very short-wave plasma oscillations for explaining the experimentally observed phenomena.

Hydrodynamic action functional and absorption of electromagnetic waves in plasma

The path integration method is used to study the absorption of waves in plasma. The absorption is considered of longitudinal electromagnetic waves as a consequence of scattering on the transverse waves, which requires the introduction of an integration with respect to a supplementary field of the vector potential. The scattering on the transverse waves becomes the determining one for a one-component plasma in the long wavelength limit. The hydrodynamic action functional is constructed for a magnetized electron-ion plasma by the method of successive integration, first with respect to “fast” fields and, next, with respect to “slow” fields. The absorption of the longitudinal waves is computed with the aid of this functional. The domains of frequencies of the order of the plasma frequency and of the order of the cyclotron frequency are considered. In comparison with the case of a free plasma, here the Coulomb logarithm is varied.

Cyclotron absorption of x rays by a classical plasma in the strong magnetic fields of neutron stars

The cyclotron absorption of electromagnetic waves in an equilibrium classical plasma in a strong magnetic field is investigated on the basis of a kinetic equation and by means of Kirchhoff's law. A study is carried out of the influence of vacuum polarization by the magnetic field on the polarization of the ordinary and extraordinary waves and on the coefficients of cyclotron absorption of these waves in the plasma. The results obtained are of interest for the theory of the emission of X-ray sources associated with neutron stars in binary systems and above all for the theory of the origin of the X rays in the spectrum of the source Her X-1.

Anomalous absorption of intense electromagnetic waves in plasma at high magnetic fields

The authors present conclusive evidence of anomalous absorption of an intense RHCP wave at high magnetic fields omega ce/ omega >1, where omega ce and omega are the electron cyclotron frequency and the frequency of the electromagnetic wave.

Gyro-resonance absorption of plasma waves in the corona and the fine structure of solar radio bursts

We consider the important part played by plasma wave absorption at the higher harmonics of the electron gyrofrequency (under conditions of the so-called double plasma resonance) in the solar corona. An explanation is proposed for the fine structure of Type III bursts on the basis of this effect.

Concerning the effect of collisions on the absorption of plasma waves

Concerning the effect of collisions on the absorption of plasma waves

General Characteristics of Vavilov-Cherenkov Radiation

The theory of radiation moving at superlight velocities is explained and fundamental equations which describe the general characteristics of the radiation are given. The energy losses of a charged particle moving in a plasma in the absence of external magnetic fields are discussed. The absorption of plasma waves in the plasma itself is shown to be conditioned by a reverse Cherenkov effect. The methods of heating plasma by an external beam of fast charged particles and by magneto-acoustic waves are described. (C.J.G.)

Test Particles in a Completely Ionized Plasma

Starting from the Liouville equation, a chain of equations is obtained by integrating out the coordinates of all but one, two, etc., particles. One ``test'' particle is singled out initially. All other ``field'' particles are assumed to be initially in thermal equilibrium. In the absence of external fields, the chain of equations is solved by expanding in terms of the parameter g = 1/nLD3. For the time evolution of the distribution function of the test particle, an equation is obtained whose asymptotic form is of the usual Fokker-Planck type. It is characterized by a frictional-drag force that decelerates the particle, and a fluctuation tensor that produces acceleration and diffusion in velocity space. The expressions for these quantities contain contributions from Coulomb collisions and the emission and absorption of plasma waves. By consideration of a Maxwell distribution of test particles, the total plasma-wave emission is determined. It is related to Landau's damping by Kirchoff's law. When there is a constant external magnetic field, the problem is characterized by the parameter g, and also the parameter λ = ωc/ωp. The calculation is made by expanding in terms of g, but all orders of λ are retained. To the lowest order in g, the frictional drag and fluctuation tensor are slowly varying functions of λ. When λ ≪ 1, the modification of the collisional-drag force due to the magnetic field, is negligible. There is a significant change in the properties of plasma waves of wavelength greater than the Larmor radius which modifies the force due to plasma-wave emission. When λ ≫ 1, the force due to plasma-wave emission disappears. The collisional force is altered to the extent that the maximum impact parameter is sometimes the Larmor radius instead of the Debye length, or something in between. In the case of a slow ion moving perpendicular to the field, the collisional force is of a qualitatively different form. In addition to the drag force antiparallel to the velocity of the particle, there is a collisional force antiparallel to the Lorentz force. The force arises because the particle and its shield cloud are spiralling about field lines. The force on the particle is equal and opposite to the centripetal force acting on the ``shield cloud.'' It is much smaller than the Lorentz force.