ELECTROMAGNETIC RADIATION FROM A DIPOLE IN AN ANISOTROPIC PLASMA
The general solution to the probledn of the radiation of an electric dipole in a magnetically-biased cold plasma is presented. Since the magnetostatic field causes the plasma to be anisotropic, the far field is in general quite complicated. lt was found that several waves exist, traveling in different directions with different indices of refraction. These waves interfere to produce beats and amplitude modulation, also causing the resultant time- average energy flow to have components in other than the radial direction, a result which is contrary to the isotropic case. The propagation direction for the waves was determined with the aid of a digital computer for w/sub p//w and w/ sub g//w between zero and 2.0. ln spite of the complexity of the field, several features are evident. For the lossless case considered, the field is unbounded in certain directions for certain values of the plasma frequency and gyro- frequency. An equation is given for the directions of these singularities. In a lossy plasma these singularities no longer exist. However the field is still very large in these directions so that they may be useful for plasma diagnostics since a measurement of these directions can be easily converted to give the average plasma density. The time-average Poynting vector and the group velocity for an individual wave are shown to be purely radial although the resultant Poynting vector due to all the waves in the far zone generally has components in other directions. Various limiting cases are amenable to solution. The case of a high operating frequency is treated; it is shown that the radiation pattern is approximately identical to the isotropic case although a Faraday rotation of the field exists. The solution for very low operating frequencies is presented and the guiding nature of the magnetic field is placed in evidence, a result well khown in the study of whistlers.'' The solution for the important case of a large magnetostatic field is also presented. It was found that the timeaverage power flow is purely in the radial direction although there are two waves present in the far zone. The effect of losses was considered briefly for the case of a large magnetostatic field; the main effect was a reduction of the poles to form large lobes of the radiation pattern. The results for an infinite magnetostatic field are also applicable to a uniaxial crystal; the similarities are pointed out. (auth)
- Research Organization:
- University of Southern California, Los Angeles. Engineering Center
- DOE Contract Number:
- AF49(638)-522
- NSA Number:
- NSA-16-004908
- OSTI ID:
- 4823849
- Report Number(s):
- USCEC-79-203; AFOSR-1582
- Resource Relation:
- Other Information: Orig. Receipt Date: 31-DEC-62
- Country of Publication:
- United States
- Language:
- English
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