Theory of 2 omega(sub pe) radiation induced by the bow shock
摘要：
A new radiation emission mechanism is proposed to explain electomagnetic radiation observed at twice the electron plasma frequency, 2 omega, in the upstream region of the Earth's bow shock. This radiation had its origin at the electron foreshock boundary where energetic electron beams and intense narrow-band Langmiur waves are observed. The proposed emission mechanism results from the interaction of the electron beam and Langmuir waves that are backscattered off thermal ions. This interaction is described by a nonlinear dispersion equation which incorporates an effect owing to electron trajectory modulation by the backscattered Langmuir waves. Subsequent analysis of the dispersion equation reveals two important consequences. First, a long-wavelength electrostatic quasi-mode with frequency at 2 omegais excited, and second, the quasi-mode and the electomagnetic mode are nonlinearly coupled. The implication is that, when the excited 2 omegaquasi-mode propagates in an inhomgeneous medium with slightly decreasing density, the quasi-mode can be converted directly into an electromagnetic mode. Hense the electomagnetic radiation at twice the plasma frequency is generated. Numerical solutions of the dispersion equation with the choice of parameters that describe physical characteristics of the electron foreshock are presented, which illustrates the viability of the new mechanism.
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关键词：
Backscattering Bow Waves Coupled Modes Electromagnetic Radiation Electron Beams Nonlinear Systems Plasma Frequencies Plasma Waves Shock Waves Earth Magnetosphere
DOI：
10.1029/94JA02489
被引量：
年份：
1994
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