RADIATION FROM A CURRENT STRIP IN A UNIAXIALLY ANISOTROPIC PLASMA MEDIUM

1966 ◽  
Vol 44 (1) ◽  
pp. 207-217 ◽  
Author(s):  
S. R. Seshadri
Keyword(s):  
Radiation Resistance ◽  
Plasma Frequency ◽  
Anisotropic Plasma ◽  
Finite Width ◽  
Plasma Medium ◽  
Magnetostatic Field ◽  
Linear Current ◽  
A Current

The radiation resistance of a linear current strip of finite width immersed in a uniaxially anisotropic plasma medium is evaluated for the case in which the width of the strip is parallel to the direction of the magnetostatic field. The current on the strip is assumed to be directed along the length of the strip and hence is perpendicular to the direction of the magnetostatic field. It is assumed also that the current is constant along the width of the strip but has a triangular variation along its length. Meaningful values for the radiation resistance are obtained for all frequencies, especially for frequencies below the plasma frequency. The dependence of the radiation resistance on the frequency and the length of the strip is examined.

EFFECT OF ION SHEATH ON RADIATION IN A MAGNETOIONIG MEDIUM: II. SOURCE CURRENT PERPENDICULAR TO THE MAGNETOSTATIC FIELD

1967 ◽  
Vol 45 (2) ◽  
pp. 279-299
Author(s):  
S. R. Seshadri ◽  
K. L. Bhatnagar
Keyword(s):  
Radiation Resistance ◽  
Free Space ◽  
Magnetized Plasma ◽  
Magnetostatic Field ◽  
Source Current ◽  
Point Electric Dipole ◽  
Two Peaks ◽  
Limiting Case ◽  
Finite Extent ◽  
A Current

The radiation characteristics of current sources situated along the axis of an infinite cylindrical column of free space and surrounded by a homogeneous, loss-free magnetoionic medium are discussed for the case in which the source current is perpendicular to the magnetostatic field. The static magnetic field is assumed to be parallel to the axis of the free-space column, which is an idealization of the ion sheath formed around the antenna in the ionosphere. Both a point electric dipole and a finite and continuous array of the same are investigated. The dependence of the radiation resistance of these sources on the frequency and the ion-sheath thickness is examined. Even in the limiting case of vanishing thickness of the ion sheath, the radiation resistances of these sources are found to be different from those corresponding to an unbounded plasma. In contrast to those in an unbounded magnetoplasma, the radiation resistance remains finite for all frequencies. For the source of finite extent having a current distribution that falls off sufficiently rapidly towards the ends, the radiation resistance is quite insensitive to the changes in the thickness of the ion sheath.The radiation-resistance curve, in general, has two peaks at the so-called dipolar resonant frequencies, which depend primarily on the strength of the magnetostatic field. These dipolar resonances, which are quite analogous to those in an axially magnetized plasma column, are found to become sharper as the radius of the free-space column becomes smaller.

RADIATION FROM A STRIP OF ELECTRIC CURRENT IN A MAGNETOIONIC MEDIUM

1967 ◽  
Vol 45 (5) ◽  
pp. 1675-1691
Author(s):  
A. D. Wunsch
Keyword(s):  
Magnetic Field ◽  
Resonance Frequency ◽  
Electric Current ◽  
Static Magnetic Field ◽  
Radiation Resistance ◽  
Finite Width ◽  
Hybrid Resonance ◽  
Wide Range ◽  
Field Integral ◽  
A Current

The radiation resistance of a strip of electric current immersed in a cold magnetoplasma is investigated. The current is assumed to flow in a direction perpendicular to the static magnetic field. Integral expressions are obtained for the radiation resistance of a Hertzian dipole and for a current strip of finite width and length. Numerical results covering a wide range of frequencies are presented for both of the sources. It is shown that there are two frequency ranges where the radiation resistance of the Hertzian dipole is infinite, while the radiation resistance of the strip is finite everywhere except at the upper hybrid resonance frequency. The way in which the length of the strip influences its radiation resistance is discussed.

Anomalous absorption of the circularly polarized electromagnetic beams near the plasma frequency in a magnetized electron plasma

2007 ◽  
Vol 73 (3) ◽  
pp. 315-330 ◽  
Author(s):  
S. R. SESHADRI
Keyword(s):  
Resonant Frequency ◽  
Plasma Frequency ◽  
Unit Length ◽  
Plane Waves ◽  
Electron Plasma ◽  
Magnetostatic Field ◽  
Power Absorption ◽  
Circularly Polarized ◽  
Focused Beams ◽  
Electromagnetic Beams

AbstractThe propagation of circularly polarized electromagnetic beams along the magnetostatic field in an electron plasma is investigated. As a consequence of a strong interaction with the medium, the beam spreads rapidly on propagation near the cutoff frequencies and the cyclotron resonant frequency of the corresponding plane waves, as well as near the plasma frequency. The power absorption for unit length near the cyclotron frequency and the plasma frequency are determined. For tightly focused beams, there is significant power absorption near the plasma frequency as compared with that at the cyclotron resonant frequency.

scholarly journals Plasma Damping of Gravitational Waves

1990 ◽  
Vol 142 ◽  
pp. 62-62
Author(s):  
C. Sivaram
Keyword(s):  
Neutron Star ◽  
Magnetic Fields ◽  
Gravitational Waves ◽  
Plasma Frequency ◽  
Landau Damping ◽  
Plasma Medium ◽  
Plane Gravitational Waves

The possibility of the damping of plane gravitational waves while propagating in a plasma medium is considered. The gravitational plasma frequency, is for a neutron star medium ~ 103Hz, which is the same as the frequency of the gravitational waves emitted by a collapsing star. So resonant damping of such waves within a collapsing star is probable. Estimates are made for the damping length for dense and dilute plasmas (also in the presence of magnetic fields). Analogies with Landau damping are made. Applications to other astrophysical situations are outlined.

DIFFRACTION BY A CONDUCTING HALF-PLANE IN AN ANISOTROPIC PLASMA

1964 ◽  
Vol 42 (8) ◽  
pp. 1455-1468 ◽  
Author(s):  
E. V. Jull
Keyword(s):  
Magnetic Field ◽  
Half Plane ◽  
Scattered Field ◽  
Plane Electromagnetic Wave ◽  
Plane Waves ◽  
Angular Spectrum ◽  
Anisotropic Plasma ◽  
Angle Of Incidence ◽  
Dual Integral Equations ◽  
Magnetostatic Field

The diffraction of a plane electromagnetic wave by a perfectly conducting half-plane in an anisotropic plasma is considered. The plasma is characterized by a permittivity tensor and the wave is assumed to propagate in a direction normal to the magnetostatic field and the diffracting edge, but its angle of incidence is otherwise arbitrary. Only the H-polarized wave of the incident field, which has a single magnetic field component parallel to the edge, is affected by the anisotropy and the analysis is restricted accordingly. Representing the scattered field as an angular spectrum of plane waves leads to dual integral equations from which an expression for the scattered field is obtained. The total field is then reduced to Fresnel integrals and its far-field behavior is investigated. Agreement with Seshadri and Rajagopal's result for a wave normally incident on the conductor, which was obtained by using the Wiener–Hopf technique, is found. The differences between isotropic and anisotropic solutions to this problem, which arise from the differing boundary conditions on the tangential magnetic field, are examined.

External and Internal Solutions for the Twisted, Flux Tube, Prominence Model

1994 ◽  
Vol 144 ◽  
pp. 345-347
Author(s):  
N. Cartledge ◽  
A. W. Hood
Keyword(s):  
Flux Tube ◽  
Free Field ◽  
Force Balance ◽  
Constant Current ◽  
Magnetic Flux Tube ◽  
Finite Width ◽  
Vertical Force ◽  
Constant Current Density ◽  
Internal Region ◽  
A Current

AbstractWe consider a model for the support of a prominence sheet in a twisted magnetic flux tube. Solutions for the equilibrium of the sheet in a constant current density force-free field, as given by Ridgwayet al. (1991) are considered and extended to include a current sheet of finite height.Next we consider the internal region of the prominence by “stretching” the sheet to a finite width. We can analytically select solutions for the field in this region that match onto the external force-free solutions at the edge of the prominence.Horizontal and vertical force balance for this internal region then determines profiles for the pressure and density and the corresponding temperature may be evaluated.

RADIATION FROM A CURRENT FILAMENT CLAD BY AN ANISOTROPIC PLASMA SHEATH

1963 ◽  
Vol 41 (6) ◽  
pp. 858-862
Author(s):  
Yujiro Ohba
Keyword(s):  
Radiation Field ◽  
Linear Polarization ◽  
Plasma Sheath ◽  
Anisotropic Plasma ◽  
Far Field ◽  
Direction Parallel ◽  
Current Filament ◽  
Te And Tm Modes ◽  
Elliptically Polarized ◽  
A Current

The radiation field from a plasma-clad filament carrying a current I0 exp (−jkzz + jωt) is calculated. The plasma, which is finite in thickness, is magnetized in the direction parallel to the current filament. The field outside the plasma sheath is expressed by a combination of TE and TM modes, and in general the field is elliptically polarized. The conditions for circular and linear polarization in the far field are related to the thickness of the plasma sheath and the wave constants of the plasma.

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