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.

EFFECT OF ION SHEATH ON RADIATION IN A MAGNETOIONIC MEDIUM: I. SOURCE CURRENT PARALLEL TO THE MAGNETOSTATIC FIELD

1966 ◽  
Vol 44 (7) ◽  
pp. 1401-1418
Author(s):  
S. R. Seshadri ◽  
K. L. Bhatnagar
Keyword(s):  
Point Source ◽  
Electric Current ◽  
Finite Length ◽  
Current Distribution ◽  
Radiation Resistance ◽  
Free Space ◽  
Sheath Thickness ◽  
Radiation Characteristics ◽  
Magnetostatic Field ◽  
Source Current

The radiation characteristics of an axially oriented point source of electric current and a filament of finite length with a triangular current distribution are treated for the case in which these sources are situated at the center of an infinite cylindrical column of free space and surrounded by a homogeneous, loss-free magnetoionic medium. The direction of the magnetostatic field is assumed to be parallel to the axis of the free-space column which is an idealization for the geometry of the ion sheath formed around the antenna in the ionosphere. The dependence of the radiation resistance of these sources on the frequency and the ion-sheath thickness is examined. It is found that, within the framework of the classical magnetoionic theory, the radiation resistance of even a point source of electric current remains finite for all frequencies, provided the ion-sheath effects are included. Also the radiation resistance of a finite-length filament with a triangular current distribution is found to be insensitive to the changes in the thickness of the ion sheath. This result is in conformity with the experimental observations, which indicate no data variations correlated with the changes in the thickness of the ion sheath.

Nonlinear waves in a magnetized plasma: periodicity analysis

1980 ◽  
Vol 23 (1) ◽  
pp. 71-89 ◽  
Author(s):  
P. C. Clemmow ◽  
R. D. Harding
Keyword(s):  
Periodic Solutions ◽  
Quantitative Agreement ◽  
Laboratory Frame ◽  
Magnetized Plasma ◽  
Magnetostatic Field ◽  
First Order ◽  
Periodicity Analysis ◽  
Arbitrary Amplitude ◽  
Direct Numerical Integration ◽  
Limiting Case

The propagation of a superluminous plane wave of fixed profile through a cold electron plasma, in a direction perpendicular to the ambient magnetostatic field, is considered. The polarization is such that the electric vector has no component parallel to the magnetostatic field. The analysis is referred to the frame of reference in which all the field quantities are uniform in space, and the exact governing equations are cast into the form of an autonomous system of four nonlinear, first-order, coupled differential equations. The equations contain the parameter n that specifies the wave speed, c/n, in the laboratory frame, and inspection reveals that the limiting case n = 0 admits two exact solutions, which are monochromatic, of arbitrary amplitude, and recover the standard solutions of linear theory in the small-amplitude limit. The possibility of the existence of corresponding period solutions for the case n ≫ 1 is then investigated by a perturbation treatment. I t is found that the analysis can be carried through explicitly, and, to the first order in n, the outcome confirms the existence of periodic solutions, and yields the dependence of the period'on an amplitude parameter. The results are checked against a direct numerical integration procedure that incorporates a method of searching for periodic solutions, and close quantitative agreement is found for sufficiently small values of n.

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.

scholarly journals Sliding Contacts in Planetary Magnetospheres

Symmetry ◽  
2021 ◽  
Vol 13 (2) ◽  
pp. 283
Author(s):  
Elena Belenkaya ◽  
Igor Alexeev
Keyword(s):  
Large Scale ◽  
Strong Field ◽  
Magnetized Plasma ◽  
Sliding Contacts ◽  
Radio Emissions ◽  
Planetary Magnetospheres ◽  
Current Task ◽  
Surrounding Space ◽  
Non Local ◽  
A Current

In the planetary magnetospheres there are specific places connected with velocity breakdown, reconnection, and dynamo processes. Here we pay attention to sliding layers. Sliding layers are formed in the ionosphere, on separatrix surfaces, at the magnetopauses and boundaries of stellar astrospheres, and at the Alfvén radius in the equatorial magnetosphere of rapidly rotating strongly magnetized giant planets. Although sliding contacts usually occur in thin local layers, their influence on the global structure of the surrounding space is very great. Therefore, they are associated with non-local processes that play a key role on a large scale. There can be an exchange between different forms of energy, a generation of strong field-aligned currents and emissions, and an amplification of magnetic fields. Depending on the conditions in the magnetosphere of the planet/exoplanet and in the flow of magnetized plasma passing it, different numbers of sliding layers with different configurations appear. Some are associated with regions of auroras and possible radio emissions. The search for planetary radio emissions is a current task in the detection of exoplanets.

scholarly journals X.—On Wollaston's Argument from the Limitation of the Atmosphere, as to the Finite Divisibility of Matter

1845 ◽  
Vol 16 (1) ◽  
pp. 79-86
Author(s):  
George Wilson
Keyword(s):  
Free Space ◽  
Earth’S Atmosphere ◽  
Earth's Atmosphere ◽  
The Law ◽  
Finite Extent

In the year 1822, Dr Wollaston published a remarkable paper “on the finite extent of the atmosphere.” Its object is to establish, by observations on the motions of certain of the heavenly bodies, that our atmosphere does not extend into free space, and to deduce from this limitation in its extent, the conclusion, that the air necessarily consists of particles “no longer divisible by repulsion of their parts;” i. e. of true atoms. From this there is the further inference, that, “since the law of definite proportions discovered by chemists, is the same for all kinds of matter, whether solid or fluid, or elastic, if it can be ascertained that any one body consists of particles no longer divisible, we then can scarcely doubt that all other bodies are similarly constituted.” In other words, the existence of a limit to the earth's atmosphere is declared to supply a demonstration of the finite divisibility of matter.

Theory of parametric resonance in a current carrying magnetized plasma

1979 ◽  
Vol 22 (6) ◽  
pp. 1154 ◽  
Author(s):  
Yu. M. Aliev ◽  
V. Stefan
Keyword(s):  
Parametric Resonance ◽  
Magnetized Plasma ◽  
A Current
Sign in / Sign up

Export Citation Format

Share Document