Čerenkov radiation within the Earth's upper atmosphere
TL;DR: A brief review of Cerenkov radiation within the upper atmospheric plasma has been presented in this article, where the results of analysis about the nature and characteristics of VLF hisses in terms of incoherent Cererkov radiation are given in a concise manner.
Abstract: A brief review of Cerenkov radiation within the upper atmospheric plasma has been presented. Different attempts in this context are systematically discussed. The results of analysis about the nature and characteristics of VLF hisses in terms of incoherent Cerenkov radiation are given in a concise manner. The occurrence of resonance cone has also been reported.
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26 Dec 1962
TL;DR: In this article, the authors investigated the radiation from a point charge moving uniformly in a plasma, when the charge is moving in the direction of an external magnetic field, and obtained two sets of values of these parameters, the frequency and the angular spectrum of the emitted radiation.
Abstract: The radiation from a point charge moving uniformly in a plasma is investigated when the charge is moving in the direction of an external magnetic field. In general, there are two modes, for each of which all the components of the electric and magnetic field are present. The two parameters of interest in this problem are the ratio of the velocity of the charges to the free-space velocity of electromagnetic waves, and the ratio of the gyromagnetic frequency to the plasma frequency of the electrons. For two sets of values of these parameters, the frequency and the angular spectrum of the emitted radiation are obtained. In certain cases, as many as three Cherenkov rays are found to propagate in the same direction; these multiple-rays, however, correspond to different frequency components and to different modes of propagation. The motivation for this investigation is indicated briefly. (auth)
13 citations
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TL;DR: In this article, the dispersion relations and the potential of a point charge in a current-carrying non-Maxwellian plasma with a beamlike or a long flat tail of the electron distribution functions are investigated with the approximation of a large magnetostatic field.
Abstract: Properties of resonance cones in non-Maxwellian plasmas are examined and compared with those in Maxwellian plasmas. The dispersion relations and the potential of a point charge in a current-carrying non-Maxwellian plasma with a beamlike or a long flat tail of the electron distribution functions are investigated with the approximation of a large magnetostatic field. In the case of a beam, when the beam velocity is well above the thermal velocities of the beam and bulk electrons, the Cerenkov instability occurs. In this case the wave number spectrum k∥ > ω/νb becomes unstable, where νb is the beam velocity, ω is the frequency, and k∥ is the wave number parallel to the magnetic field. The Cerenkov instability causes strong radiation near a conical surface called the Cerenkov cone. When νb is not very large, the Cerenkov cone angle is found to be considerably smaller than the resonance cone angle, thus there are two distinct angles corresponding to the Cerenkov and resonance cones, where the radiation peaks. The Cerenkov cone peak grows with increasing distance from the source, while the resonance cone peak decays. For the situations when the resonance cone peak is not affected by the Cerenkov instability, we have compared the angular shifts of the resonance cone peaks caused by the same current in Maxwellian and non-Maxwellian plasmas. This comparison throws light on the resonance cone technique for measuring magnetic field-aligned currents in plasmas. It is found that a long flat tail to the bulk electron distribution function gives a characteristic split to the resonance cone peak in the downstream of the electron flow, an observation of this split can be used as an indication of the existence of the long tail.
5 citations
01 Mar 1958
TL;DR: In this paper, the Cerenkov radiation emitted by a fast charged particle moving through one medium and in the vicinity of another medium has been theoretically investigated, employing the invariance of the phenomenological electrodynamic equations of Maxwell.
Abstract: The Cerenkov radiation emitted by a fast charged particle moving through one medium and in the vicinity of another medium has been theoretically investigated, employing the invariance of the phenomenological electrodynamic equations of Maxwell. A simple geometry has been considered, this being the case of two coaxial dielectrics and permeable cylinders with a common cylindrical interface and a charged particle moving along their common axis. The results obtained have been discussed with special reference to the case of Cerenkov radiation at microwave and radio-frequency regions. The effect of the phenonema and coherence on the output of the emitted radiation in these cases has been briefly outlined.
4 citations
01 Feb 1966
TL;DR: In this article, it was shown that Cerenkov radiation in the extraordinary mode cannot be excited by particles travelling with speeds less than the geometric mean of the thermal speed and the speed of light in vacuum.
Abstract: The radiation emitted by a charged particle moving with uniform speed parallel to an infinite magnetic field in a hot plasma is evaluated when the phase speed of the excited waves is very much greater than the thermal speed. It is found that Cerenkov radiation in the extraordinary mode cannot be excited by particles travelling with speeds less than the geometric mean of the thermal speed and the speed of light in vacuum. The total energy emitted in the form of plasma waves exceeds that excited in the extraordinary wave when the particle moves slower than ?2 times the minimum speed capable of exciting the extraordinary wave radiation.
3 citations