Theory of magnetosonic wave—plateau shocks driven by upper-hybrid waves

1990 ◽  
Vol 44 (3) ◽  
pp. 489-506 ◽  
Author(s):  
N. N. Rao
Keyword(s):  
Wave Structure ◽  
Present Theory ◽  
Finite Amplitude ◽  
Magnetized Plasma ◽  
Magnetosonic Wave ◽  
Number Density ◽  
Dense Structure ◽  
Hybrid Waves ◽  
The Magnetic Field ◽  
Front Region

The existence as well as the structure of magnetosonic wave-plateau shocks driven by upper-hybrid waves in a two-component electron-ion magnetized plasma is analysed. In the incident region the field quantities have a standing-wave structure, whereas in the evanescent region they monotonically reach constant values. The plasma flow velocity undergoes a transition from submagnetosonic (in the evanescent region) to supermagnetosonic (in the incident region) values via the magnetosonic point. The number density (or the magnetic field) across the shock-front region has a steep gradient and connects a rarefaction (under-dense) wave in the incident region to a shelf-like (over-dense) structure in the evanescent region, where the upper-hybrid electric field drops to zero monotonically. For the case of small- but finite-amplitude shocks the detailed structures of the profiles are obtained analytically. For large-amplitude shocks the profiles are computed using numerical methods. An extension of the present theory as well as some possible applications are pointed out.

Solitary Alfvén waveguide structures in a magnetized plasma

1980 ◽  
Vol 24 (1) ◽  
pp. 157-162 ◽  
Author(s):  
J. P. Sheerin ◽  
R. S. B. Ong
Keyword(s):  
Magnetic Field ◽  
Solitary Wave ◽  
Field Line ◽  
Magnetic Field Line ◽  
Axial Symmetry ◽  
Wave Structure ◽  
Magnetized Plasma ◽  
Alfven Wave ◽  
Wave Forms ◽  
The Magnetic Field

A nonlinear Alfvén wave structure with axial symmetry about the line of force of an ambient magnetic field is presented. The solitary wave forms a ‘ring’ shaped waveguide along the magnetic field line.

Excitation of upper-hybrid waves by a thermal parametric instability

1983 ◽  
Vol 30 (3) ◽  
pp. 463-478 ◽  
Author(s):  
M. C. Lee ◽  
S. P. Kuo
Keyword(s):  
Ohmic Heating ◽  
Parametric Instability ◽  
Wave Interaction ◽  
Present Theory ◽  
Magnetized Plasma ◽  
Coupling Mechanism ◽  
Ionospheric Heating ◽  
Plasma Line ◽  
Thermal Parametric Instability ◽  
Hybrid Waves

A purely growing instability characterized by a four-wave interaction has been analysed in a uniform, magnetized plasma. Up-shifted and down-shifted upper-hybrid waves and a non-oscillatory mode can be excited by a pump wave of ordinary rather than extraordinary polarization in the case of ionospheric heating. The differential Ohmic heating force dominates over the ponderomotive force as the wave–wave coupling mechanism. The beating current at zero frequency produces a significant stabilizing effect on the excitation of short-scale modes by counterbalancing the destabilizing effect of the differential Ohmic heating. The effect of ionospheric inhomogeneity is estimated, showing a tendency to raise the thresholds of the instability. When applied to ionospheric heating experiments, the present theory can explain the excitation of field-aligned plasma lines and ionospheric irregularities with a continuous spectrum ranging from metre-scale to hundreds of metre-scale. Further, the proposed mechanism may become a competitive process to the parametric decay instability and be responsible for the overshoot phenomena of the plasma line enhancement at Arecibo.

Stimulated backscattering of electromagnetic waves from ion–ion hybrid waves in a magnetized plasma

1975 ◽  
Vol 14 (2) ◽  
pp. 245-253 ◽  
Author(s):  
Kai Fong Lee
Keyword(s):  
Magnetic Field ◽  
Electromagnetic Waves ◽  
Magnetized Plasma ◽  
Threshold Power ◽  
Lower Hybrid ◽  
Stimulated Scattering ◽  
Electrostatic Waves ◽  
Hybrid Frequency ◽  
Hybrid Waves ◽  
The Magnetic Field

In a high-density magnetized plasma composed of two ion species of different charge-to-mass ratios, electrostatic waves propagating across the magnetic field exhibit a resonance at the Buchsbaum or ion-ion hybrid frequency, in addition to the resonances at the upper and lower hybrid frequencies. In this paper, the possibility of stimulated scattering of electromagnetic waves incident normal to the magnetic field from electrostatic waves at the ion-ion hybrid frequency is investigated. Based on the cold-plasma equations, it is found that such a process is theoretically possible. Formulas for the threshold power and growth rate are obtained, which show that the threshold power is much greater, and the growth rate much less, than those of stimulated scattering from upper and lower hybrid waves.

Production of plasma vortices by lower-hybrid waves

1981 ◽  
Vol 26 (2) ◽  
pp. 359-367 ◽  
Author(s):  
M. Y. Yu ◽  
P. K. Shukla ◽  
H. U. Rahman
Keyword(s):  
Plasma Heating ◽  
Finite Amplitude ◽  
Current Drive ◽  
Lower Hybrid ◽  
Magnetic Fluctuations ◽  
Field Diffusion ◽  
Modulational Instabilities ◽  
Hybrid Waves ◽  
Plasma Vortices ◽  
Lower Hybrid Waves

Nonlinear excitation of electrostatic and magnetostatic zero-frequency modes by finite-amplitude lower-hybrid waves is considered. It is found that modulational instabilities can give rise to enhanced plasma vortices. Dispersion relations, as well as analytical expressions for the growth rates, are obtained. The enhanced vortices may cause anomalous cross-field diffusion which can affect plasma confinement in tokamak devices when lower-hybrid waves are used for plasma heating or current drive. We found that magnetic fluctuations associated with the parametrically driven magnetostatic mode are of particular importance in tokamak plasmas.

scholarly journals Hydromagnetic dynamos in rotating spherical fluid shells in dependence on the Prandtl number, density stratification and electromagnetic boundary conditions

2014 ◽  
Vol 44 (4) ◽  
pp. 293-312 ◽  
Author(s):  
Tomáš Šoltis ◽  
Ján Šimkanin
Keyword(s):  
Magnetic Field ◽  
Electrical Conductivity ◽  
Magnetic Fields ◽  
Prandtl Number ◽  
Inner Core ◽  
Polar Regions ◽  
Number Density ◽  
Magnetic Diffusion ◽  
Spherical Fluid ◽  
The Magnetic Field

Abstract We present an investigation of dynamo in a simultaneous dependence on the non-uniform stratification, electrical conductivity of the inner core and the Prandtl number. Computations are performed using the MAG dynamo code. In all the investigated cases, the generated magnetic fields are dipolar. Our results show that the dynamos, especially magnetic field structures, are independent in our investigated cases on the electrical conductivity of the inner core. This is in agreement with results obtained in previous analyses. The influence of non-uniform stratification is for our parameters weak, which is understandable because most of the shell is unstably stratified, and the stably stratified region is only a thin layer near the CMB. The teleconvection is not observed in our study. However, the influence of the Prandtl number is strong. The generated magnetic fields do not become weak in the polar regions because the magnetic field inside the tangent cylinder is always regenerated due to the weak magnetic diffusion.

scholarly journals Lepton-driven Nonresonant Streaming Instability

2021 ◽  
Vol 923 (2) ◽  
pp. 208
Author(s):  
Siddhartha Gupta ◽  
Damiano Caprioli ◽  
Colby C. Haggerty
Keyword(s):  
Magnetic Field ◽  
Laboratory Experiments ◽  
Magnetized Plasma ◽  
Ion Current ◽  
Pulsar Wind Nebulae ◽  
Particle In Cell ◽  
Streaming Instability ◽  
Electrons And Positrons ◽  
Pulsar Wind ◽  
The Magnetic Field

Abstract A strong super-Alfvénic drift of energetic particles (or cosmic rays) in a magnetized plasma can amplify the magnetic field significantly through nonresonant streaming instability (NRSI). While the traditional analysis is done for an ion current, here we use kinetic particle-in-cell simulations to study how the NRSI behaves when it is driven by electrons or by a mixture of electrons and positrons. In particular, we characterize the growth rate, spectrum, and helicity of the unstable modes, as well the level of the magnetic field at saturation. Our results are potentially relevant for several space/astrophysical environments (e.g., electron strahl in the solar wind, at oblique nonrelativistic shocks, around pulsar wind nebulae), and also in laboratory experiments.

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