Wave dispersoin and resonant deposition profiles of electron-cyclotron Gaussian beams in toroidal plasmas

1995 ◽  
Vol 53 (3) ◽  
pp. 345-364 ◽  
Author(s):  
S. Cirant ◽  
S. Nowak ◽  
A. Orefice
Keyword(s):  
Electromagnetic Waves ◽  
Cyclotron Frequency ◽  
Three Dimensional ◽  
Electron Cyclotron ◽  
Gaussian Beams ◽  
Beam Structure ◽  
Toroidal Plasmas ◽  
Optical Propagation ◽  
Equilibrium Configurations ◽  
Magnetic Equilibrium

A peculiarity of the quasi-optical propagation of a Gaussian beam of electromagnetic waves is that it requires a treatment taking account, step by step, of all of its rays together. The dispersion relation from which such a ray- tracing may be deduced is in fact characterized not only by the medium where the beam is launched but also by the intrinsic beam structure. The behaviour of three-dimensional Gaussian beams in the electron-cyclotron frequency range is considered, with particular attention paid to their propagation in toroidal plasmas of fusion interest (with ITER-like parameters and various magnetic equilibrium configurations), to the generality of their launching conditions and to their power deposition profiles around resonant layers.

scholarly journals Collisional and resonance absorption of electromagnetic waves in a weakly collisional, inhomogeneous magnetoplasma slab

2020 ◽  
Vol 9 (2) ◽  
pp. 25-30
Author(s):  
F. Rawwagah ◽  
M. Al-Ali ◽  
A. Al-Khateeb ◽  
M. Bawa'aneh
Keyword(s):  
Magnetic Field ◽  
Electromagnetic Waves ◽  
Electron Cyclotron Resonance ◽  
Cyclotron Frequency ◽  
Low Frequency ◽  
Electron Cyclotron ◽  
The Body ◽  
Absorption Bands ◽  
Dc Magnetic Field ◽  
Frequency Branch

Absorbance of normally incident electromagnetic wave on a cold, weakly collisional, and inhomogeneous magnetoplasma slab is investigated. The plasma density is Budden-like sinusoidal profile, where the inhomogeniety is treated as a multilayered system of homogeneous sub-cells within the transfer matrix technique. For incident wave frequencies much above the ion cyclotron frequency, only right hand circularly polarized waves are relevant for wave propagation parallel to a static magnetic field. Calculations are performed in normalized parameters, that make the results suitable for many applications including atmospheric and laboratory plasmas. The presence of the dc-magnetic field leads to the formation of two absorption bands explained by plasma collisional dissipation and electron cyclotron resonance in the low frequency branch of the $R$-wave below the electron cyclotron frequency. The transmittance shows the emergence of the low frequency electron cyclotron wave, which becomes a Whistler mode at very low frequency. More detailed discussion on the effect of plasma collisionality, inhomogeneity, and dc-magnetic field on the propagation characteristics is given at the relevant place within the body of the manuscript.

Quasi-optical description of reflection, focusing and plasma cut-offs of electron cyclotron Gaussian beams

1997 ◽  
Vol 57 (2) ◽  
pp. 349-361 ◽  
Author(s):  
S. NOWAK ◽  
A. OREFICE
Keyword(s):  
Electromagnetic Waves ◽  
Solution Method ◽  
Electron Cyclotron ◽  
Gaussian Form ◽  
Toroidal Plasmas ◽  
Beam Focusing ◽  
Transparent Media ◽  
Isotropic Media ◽  
Physical Features

In the analysis of the propagation of electromagnetic waves in the electron cyclotron frequency range, in both isotropic media and magnetoactive plasmas, the role of diffractive effects, which are not accounted for by geometrical optics, may no longer be neglected when highly collimated beams are to be employed. Moreover, when lenses, mirrors, refractive gradients and/or wave cut-offs are placed along the beam trajectory, the very concept of independent optical rays tends to introduce singularities, which do not always correspond to physical features. A quasi-optical approach has previously been shown to present the advantage of allowing a description (at the lowest order of approximation) of the diffractive widening of the beam. The specific aim of this paper is to test, when reflection, refraction or beam focusing indicates the need for particular attention, the solution method employed within such an approach. The results presented here concern the propagation and power deposition profiles, in a number of crucial physical situations, of narrow electron cyclotron beams launched, in Gaussian form, either into isotropic transparent media or through anisotropic toroidal plasmas of fusion interest.

Inhomogeneity effects on the absorption of electromagnetic high-frequency waves by magnetized Maxwellian plasmas

1990 ◽  
Vol 43 (3) ◽  
pp. 335-356 ◽  
Author(s):  
R. A. Caldela Fo ◽  
R. S. Schneider ◽  
L. F. Ziebell
Keyword(s):  
Magnetic Field ◽  
High Frequency ◽  
Electromagnetic Waves ◽  
Cyclotron Frequency ◽  
Electron Cyclotron ◽  
Temperature Anisotropy ◽  
Plasma Parameters ◽  
Electron Cyclotron Frequency ◽  
High Frequency Waves ◽  
The Magnetic Field

Inhomogeneity effects on the absorption of high-frequency electromagnetic waves by magnetized Maxwellian plasmas are considered, and in particular the propagation and absorption of the ordinary and extraordinary modes propagating perpendicularly to the magnetic field are analysed. We show that, for small values of the ratio of the electron plasma frequency to the electron-cyclotron frequency, the inhomogeneity effects are more important for the ordinary mode, and that for values of this ratio close to or greater than unity the effects become pronounced for the extraordinary mode. It is also shown that, for a given value of this ratio, and for a fixed value of the ratio of electron-cyclotron frequency to wave frequency, the inhomogeneity effects tend to increase as the ambient magnetic field decreases. The temperature dependence of the effect, the dependence on the direction of propagation l'elative to the inhomogeneity, the influence of temperature anisotropy, and the isolated contribution of the gradients of different plasma parameters are investigated. Several circumstances in which instabilities may occur are mentioned.

scholarly journals Radial variation of whistler-mode chorus: first results from the STAFF/DWP instrument on board the Double Star TC-1 spacecraft

2005 ◽  
Vol 23 (8) ◽  
pp. 2937-2942 ◽  
Author(s):  
O. Santolík ◽  
E. Macúšová ◽  
K. H. Yearby ◽  
N. Cornilleau-Wehrlin ◽  
H. StC. K. Alleyne
Keyword(s):  
Cyclotron Frequency ◽  
Power Spectra ◽  
Double Star ◽  
Electron Cyclotron ◽  
Radial Variation ◽  
Whistler Mode ◽  
Electron Cyclotron Frequency ◽  
The Earth ◽  
First Results ◽  
Initial Results

Abstract. We use the first measurements of the STAFF/DWP instrument on the Double Star TC-1 spacecraft to investigate whistler-mode chorus. We present initial results of a systematic study on radial variation of dawn chorus. The chorus events show an increased intensity at L parameter above 6. This is important for the possible explanation of intensifications of chorus, which were previously observed closer to the Earth at higher latitudes. Our results also indicate that the upper band of chorus at frequencies above one-half of the electron cyclotron frequency disappears for L above 8. The lower band of chorus is observed at frequencies below 0.4 of the electron cyclotron frequency up to L of 11-12. The maxima of the chorus power spectra are found at slightly lower frequencies compared to previous studies. We do not observe any distinct evolution of the position of the chorus frequency band as a function of L. More data of the TC-1 spacecraft are needed to verify these initial results and to increase the MLT coverage.

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