INSTABILITY OF LANGMUIR-WAVES IN PLASMA IRRADIATED BY DIRECTED GAMMA-RAYS

In this Letter we investigate the possibility of Langmuir turbulence generation by directed gamma rays penetrating a background plasma. Turbulence is generated because Compton scattering creates superthermal electrons whose distribution can be unstable to the Cherenkov radiation of Langmuir waves. Using the Klein-Nishina cross section for relativistic Compton scattering, we calculate the momentum distribution of recoil electrons and derive the increment of instability for nonmagnetized plasma. The instability appears when there is a sufficiently narrow bump, for example, annihilation line h=mec2 with a width less than 0.3 mec2, in the gamma spectrum. © 1995 The American Physical Society.