RESEARCH NOTE: Explosive instabilities in an electron beam plasma

The generation of low-frequency oscillations by the explosive instabilities involving negative-energy or zero-energy waves in an electron beam plasma is discussed. A time-averaged system of fluid equations is used on considering nonlinear wave interactions in a uniform plasma including a rapid monoenergetic electron beam having low density. The interaction of waves far from the linear stability boundary is considered along with the nonlinear stage of the instability. It is found that an electron beam plasma is explosively unstable over a wide range of k-space. The characteristic time of a nonlinear process may be shortened if one of the coupled waves is near the linear stability boundary. Intense low-frequency oscillations are observed to be generated by explosive instabilities.