Spatial, spectral, and statistical properties of the high-frequency electrostatic fluctuations in a beam-driven turbulent plasma

The spatial, spectral, and statistical properties of the high-frequency (omega similar to omega (pe)) electrostatic fluctuations in an unmagnetized, statistically stable, beam-driven, strongly turbulent plasma are investigated experimentally and the results are compared to the two-component model of Robinson and Newman. The fluctuations are found to consist of low-level wave activity [W]similar to 10(-2)-10(-3) punctuated by semiperiodic, intense, spiky field events [W]similar to1, where [W] is the normalized wave intensity. The low-level wave activity has a spectral spread Deltak/k similar to Delta omega/omega similar to 30%, dispersion relation v(beam)similar to omega /k, and correlation length l(c)approximate to3 lambda (ES) where lambda (ES) is the electrostatic wavelength, and shows evidence of low-intensity parametric decay products. The intense field events, on the other hand, show little correlation for l>lambda (ES), have a full width at half maximum of l(f)<40<lambda>(D), where lambda (D) is the Debye length, and are nonpropagating. The results indicate that the two-component model, and the Zakharov equations to which the model was originally verified, give an accurate description of strong Langmuir turbulence. (C) 2001 American Institute of Physics. [DOI: 10.1063/1.1328356].