Weak nonlinear electromagnetic waves and low-frequency magnetic-field generation in electron-positron-ion plasmas

1988 ◽  
Vol 40 (2) ◽  
pp. 289-298 ◽  
Author(s):  
F. B. Rizzato
Keyword(s):  
Magnetic Fields ◽  
High Frequency ◽  
Electromagnetic Waves ◽  
Low Frequency ◽  
Spontaneous Generation ◽  
Magnetic Field Generation ◽  
Frequency Wave ◽  
Weakly Nonlinear ◽  
Nonlinear Localization ◽  
Electron Positron

The weakly nonlinear localization of obliquely modulated high-frequency electromagnetic waves in an electron-positron-ion plasma is considered. It is shown that the amplitude of the wave turns out to be a strongly dependent function of the angle between the slow modulations and the fast spatial variations and that the possibility appears of spontaneous generation of low-frequency magnetic fields. These magnetic fields are also functions of this angle and of the high-frequency wave polarization. The analysis of colinear modulation in electron-positron plasmas shows that some restriction must be made regarding the validity of previous calculations.

Growth of low-frequency waves due to a photon beam in a magnetized electron–positron plasma

1997 ◽  
Vol 58 (2) ◽  
pp. 345-366 ◽  
Author(s):  
QINGHUAN LUO ◽  
D. B. MELROSE
Keyword(s):  
High Frequency ◽  
Random Phase ◽  
Low Frequency ◽  
Photon Beam ◽  
Radio Waves ◽  
Wave Interactions ◽  
Frequency Wave ◽  
Pair Plasma ◽  
Electron Positron ◽  
Low Frequency Waves

The effect of a beam of radio waves of very high brightness passing through a cold, magnetized, electron–positron plasma is discussed. The properties of the natural wave modes in such a plasma are summarized, and approximate forms for the nonlinear response tensor are written down. Photon-beam-induced instabilities of low-frequency waves in the pair plasma are analysed in the random-phase approximation. When three-wave interactions involve two high-frequency waves in the same mode and a low-frequency wave in a different mode, wave–wave interactions are similar to wave–particle interactions in that photons act like particles that emit and absorb low-frequency waves. The absorption coefficients for various low-frequency waves due to a photon beam are evaluated. In a pure electron–positron plasma, photon-beam-induced instabilities can be effective only when either the high-frequency or the low-frequency waves are strongly modified by the magnetic field. The growth of the low-frequency waves is most effective when the high-frequency photon beam has a frequency close to the cyclotron frequency.

Scattering of electromagnetic waves by hybrid waves in a two-electron-temperature plasma

1991 ◽  
Vol 46 (1) ◽  
pp. 99-106 ◽  
Author(s):  
S. K. Sharma ◽  
A. Sudarshan
Keyword(s):  
Growth Rate ◽  
Electron Temperature ◽  
High Frequency ◽  
Electromagnetic Waves ◽  
Low Frequency ◽  
Lower Hybrid ◽  
Stimulated Scattering ◽  
Coupled Modes ◽  
Temperature Plasma ◽  
Electrostatic Perturbation

In this paper, we use the hydrodynamic approach to study the stimulated scattering of high-frequency electromagnetic waves by a low-frequency electrostatic perturbation that is either an upper- or lower-hybrid wave in a two-electron-temperature plasma. Considering the four-wave interaction between a strong high-frequency pump and the low-frequency electrostatic perturbation (LHW or UHW), we obtain the dispersion relation for the scattered wave, which is then solved to obtain an explicit expression for the growth rate of the coupled modes. For a typical Q-machine plasma, results show that in both cases the growth rate increases with noh/noc. This is in contrast with the results of Guha & Asthana (1989), who predicted that, for scattering by a UHW perturbation, the growth rate should decrease with increasing noh/noc.

Scattering and Modulational Instabilities in Magnetized Plasmas

1974 ◽  
Vol 29 (12) ◽  
pp. 1736-1741 ◽  
Author(s):  
M. Y. Yu ◽  
K. H. Spatschek ◽  
P. K. Shukla
Keyword(s):  
High Frequency ◽  
Electromagnetic Waves ◽  
Wave Interaction ◽  
Scattered Wave ◽  
Magnetized Plasma ◽  
Stimulated Scattering ◽  
Frequency Wave ◽  
Electrostatic Wave ◽  
Linear Current ◽  
Modulational Instabilities

The decay of a high-frequency wave into a scattered and an electrostatic wave is investigated for a homogeneous magnetized plasma. For wave propagation in arbitrary directions, an equation for the scattered wave is obtained accounting for the effect of the non-linear current density produced by the three-wave interaction process. As an illustration, the propagation of electromagnetic waves perpendicular to the external magnetic field is considered. The growth rates and thresholds for the stimulated scattering and modulational instabilities are obtained. The influence of a weak inhomogeneity is also considered.

PARTICLE ACCELERATION AND MAGNETIC FIELD GENERATION IN SHEAR-FLOWS

2014 ◽  
Vol 28 ◽  
pp. 1460195
Author(s):  
K.-I. NISHIKAWA ◽  
P. HARDEE ◽  
Y. MIZUNO ◽  
I. DUŢAN ◽  
B. ZHANG ◽  
...  
Keyword(s):  
Particle Acceleration ◽  
Magnetic Fields ◽  
Lorentz Factor ◽  
Velocity Shear ◽  
Magnetic Field Generation ◽  
Electron Positron ◽  
Relativistic Jet ◽  
Unmagnetized Plasma ◽  
Alternating Magnetic Fields ◽  
Transverse Deflection

We have investigated the generation of magnetic fields associated with velocity shear between an unmagnetized relativistic (core) jet and an unmagnetized sheath plasma by the kinetic Kelvin-Helmholtz instability for different mass ratios (m i /m e = 1, 20, and 1836) and different jet Lorentz factors. We found that electron-positron cases have alternating magnetic fields instead of the DC magnetic fields found in electron-ion cases. We have also investigated particle acceleration and shock structure associated with an unmagnetized relativistic jet propagating into an unmagnetized plasma for electron-positron and electron-ion plasmas. Strong magnetic fields generated in the trailing shock lead to transverse deflection and acceleration of the electrons. We have self-consistently calculated the radiation from the electrons accelerated in the turbulent magnetic fields for different jet Lorentz factors. We find that the synthetic spectra depend on the bulk Lorentz factor of the jet, the jet temperature, and the strength of the magnetic fields generated in the shock.

Study on Absorbing Properties of Honeycomb Absorbing Materials

2013 ◽  
Vol 815 ◽  
pp. 645-649
Author(s):  
Hui Min Sun ◽  
Zhao Zhan Gu ◽  
Ran Ran Yang
Keyword(s):  
Layer Thickness ◽  
High Frequency ◽  
Free Space ◽  
Low Frequency ◽  
Resonance Peak ◽  
Test Method ◽  
Electromagnetic Parameters ◽  
Frequency Wave ◽  
Absorbing Materials

Honeycomb absorbing materials were measured using the method of free space in this paper. The reflectance of honeycomb absorbing materials was calculated and simulated, and it was verified based on the measured results. It was demonstrated that this test method was feasible. Through studying on absorbing properties of honeycomb, the results have showed that the radar absorbing properties of honeycomb are related to electromagnetic parameters, as well as thickness of the dip-coatings. With the increase of thickness of the dipping layer, the radar absorbing capability of high frequency and low frequency wave are significantly increased. It is worth noting that the resonance peak moved to the low frequency with the increase of dipping layer thickness. These results are useful for design of honeycomb absorbing materials.

scholarly journals Simulation of non-hydrostatic gravity wave propagation in the upper atmosphere

2014 ◽  
Vol 32 (4) ◽  
pp. 443-447 ◽  
Author(s):  
Y. Deng ◽  
A. J. Ridley
Keyword(s):  
Wave Propagation ◽  
Gravity Wave ◽  
High Frequency ◽  
General Circulation ◽  
Low Frequency ◽  
Circulation Model ◽  
Horizontal Resolution ◽  
Upper Atmosphere ◽  
Cutoff Wavelength ◽  
Frequency Wave

Abstract. The high-frequency and small horizontal scale gravity waves may be reflected and ducted in non-hydrostatic simulations, but usually propagate vertically in hydrostatic models. To examine gravity wave propagation, a preliminary study has been conducted with a global ionosphere–thermosphere model (GITM), which is a non-hydrostatic general circulation model for the upper atmosphere. GITM has been run regionally with a horizontal resolution of 0.2° long × 0.2° lat to resolve the gravity wave with wavelength of 250 km. A cosine wave oscillation with amplitude of 30 m s−1 has been applied to the zonal wind at the low boundary, and both high-frequency and low-frequency waves have been tested. In the high-frequency case, the gravity wave stays below 200 km, which indicates that the wave is reflected or ducted in propagation. The results are consistent with the theoretical analysis from the dispersion relationship when the wavelength is larger than the cutoff wavelength for the non-hydrostatic situation. However, the low-frequency wave propagates to the high altitudes during the whole simulation period, and the amplitude increases with height. This study shows that the non-hydrostatic model successfully reproduces the high-frequency gravity wave dissipation.

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