プラズマ中の二つの電磁波の非線形相互作用

概要

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Recently the research of the dynamic response of plasma to high power electromagnetic waves has attracted considerable attention. The purpose of this report is to present the result of the analytical study of nonlinear interaction between two electromagnetic waves which are assumed to be incident from a vacuum to a semi-infinite, isotropic plasma. It is shown that, if the two waves have different frequency (ω_1,ω_2) each other, the second order fluctuations in electron density and electromagnetic fields with frequencies 2ω_1,2ω_2 and |ω_1±ω_2| are excited in the plasma medium. We assume that the nonlinear effect is weak, so that in the first approximation we can speak of the interaction of linear waves. We also assume that the plasma is cold and the collision frequency of the plasma is much smaller than the frequency of the incident electromagnetic waves. The difference frequency wave (|ω_1-ω_2|) is of particular interest, since it may be experience a resonance in a region, where both incident waves may be able to propagate. The resonance at the difference frequency wave takes place, if |ω_1-ω_2|=ω_p, where ω_p is the plasma frequency.
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