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, it is shown that the total power generated in this region is comparable to the observed power, and it is concluded that auroral hiss may be generated by incoherent Cerenkov radiation from electrons with energies of the order of 1 kev.
Abstract: A wideband noise known as auroral hiss is observed at very low and low frequencies at ground-based stations and on satellites at high magnetic latitudes. Several attempts have been made to explain this noise as incoherent Cerenkov radiation from energetic particles in the magnetosphere, but the conclusions were all negative, as the calculated power was several orders of magnitude below the observed power. The results of recent observations of auroral hiss and of the low-energy electrons with which this noise is strongly correlated suggest that unrealistic models were used in earlier calculations of the total power generated in the magnetosphere by an incoherent Cerenkov process. Therefore it is considered worthwhile to study the Cerenkov radiation again. This paper discusses a model for a region in space in which the auroral hiss is believed to be generated. It is shown that the total power generated in this region is comparable to the observed power, and it is concluded that auroral hiss may be generated by incoherent Cerenkov radiation from electrons with energies of the order of 1 kev.
136 citations
TL;DR: In this article, the general solution to the problem of monochromatic radiation from an electric dipole in a magnetically biased, cold, tenuous plasma is presented, and it is found that, generally, several waves exist in the radiation zone, traveling in different directions with different indices of refraction.
Abstract: The general solution to the problem of monochromatic radiation from an electric dipole in a magnetically biased, cold, tenuous plasma is presented. It is found that, generally, several waves exist in the radiation zone, traveling in different directions with different indices of refraction. For certain ranges of the plasma, gyro, and operating frequencies, the field becomes very large in certain directions compared with that in other directions, producing highly directive radiation characteristics. In general, the expression for the field is quite complicated although several special cases are treated which yield simple solutions. For high operating frequency it is found that the radiation pattern is identical to the isotropic case although a Faraday rotation takes place. Solutions are given for low and very low frequencies which place in evidence the guiding nature of the magnetostatic field. For the case of a large magnetostatic field it is shown that only two waves exist and that the time‐average power flow is purely radial.
126 citations
TL;DR: In this article, a procedure for calculating the Cerenkov and cyclotron radiation power from a spectrum of electrons in a test volume is outlined, as well as a ray-tracing routine for determining the path that the emitted power follows through the magnetosphere.
Abstract: Consideration of incoherent Cerenkov radiation from intense fluxes of electrons in the magnetosphere as a source of VLF hiss and several other emission phenomena. A procedure for calculating the Cerenkov and cyclotron radiation power from a spectrum of electrons in a test volume is outlined, as well as a ray-tracing routine for determining the path that the emitted power follows through the magnetosphere. Comparisons are made between a VLF hiss event and an energetic particle spectrum observed simultaneously with the Injun 5 spacecraft. Calculated power and fields for incoherent Cerenkov radiation are two orders of magnitude below the observed VLf hiss values, although the spectral shapes are similar. It is concluded that a partially coherent or amplified Cerenkov source or an instability is located in the altitude range from 3000 to 10,000 km. Calculations regarding Cerenkov radiation as a possible source for other wave phenomena indicate that upper hybrid resonance noise and fast hisslers may be understood in terms of incoherent Cerenkov radiation, but that V-shaped VLF hiss, saucers, ELF hiss, and Io-related Jovian decametric radiation may not.
95 citations
TL;DR: Ionospheric electric and electromagnetic waves broadband characteristics, investigating auroral hiss and LHR noise were discussed in this article, where the authors investigated the effect of LHR noises.
Abstract: Ionospheric electric and electromagnetic waves broadband characteristics, investigating auroral hiss and LHR noise
89 citations
TL;DR: In this article, the authors discussed the possibility that Cerenkov radio emission by auroral particles approaching the earth may contribute to the level of the continuous component of atmospheric radio noise observed at frequencies of hundreds of kilocycles per second.
87 citations