High-frequency radiation from strong density fluctuations in a turbulent plasma, ch.8

The spectrum of e.m. radiation emitted by a hot hydrogen plasma yields information on non-thermal fluctuations in a turbulent heating experiment. Its frequency spectrum contains frequencies below the electron plasma frequency fsub(pe) during the first half microsecond when plasma turbulence is characterized by streaming instabilities. When after a few microseconds the ion temperature approaches the electron temperature, a current stagnation is observed. Then the spectrum consists of clear maxima at the plasma frequency and its harmonics up to fsub(pe). It is demonstrated that radiation can result from strongly anharmonic electron oscillations, which can be as high as deltan/n approximately 0.4, trapped in long-lived solitary density depressions. Above 5 fsub(pe) enhanced Bremsstrahlung has to be taken into account. (Auth.)