Number of wavelengths in the system (mode number; m) = 16 Amplitude of the magnetic field of the pump wave = 0-1 External magnetic field = 1.0 The computer code is a full electromagnetic particle code, called KEMPO (Matsumoto and Omura, 1985). The KEMPO is a two-and-half dimensional code, but is used as one-and-two-half D for the present study. In the code, electron dynamics in their self-consistent electromagnetic fields are traced together with the nonlinear evolution of the EM fields. Total number of super-electrons handled in the present simulation is 32,768. 4. SIMULATION RESULTS Figure 3 shows the results of the dispersion analysis of the electromagnetic electric field component Ey and electrostatic electric component Ex. The former Ev component is decomposed into positive and negative k components separately. As seen in the figure, the w-k diagram of Ey with positive k's clearly shows that a large amplitude O-mode wave with m = 16 is propagating in the system as a pump wave. The other two diagrams show that both the back-scattered O-mode waves m = — 14, —15, —16 and —17 and the electrostatic electron cyclotron wave with m = 30 are excited. The most intense back-scattered wave is that with k = -14. The examination of the frequencies of the most intense back-scattered wave and the excited wave shows that the necessary conditions of energy and momentum conservation law of the resonant three wave interaction of the following form is satisfied. where the suffixes o, i, and e denote the pump, idler and excited wave components, respectively. Figure 4 shows a time history of energy density of the electric field of the mode 16, 14 and 30, respectively.
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