Princeton Plasma Physics Laboratory (PPPL) Theory Seminar

Scrape-off layer plasmas feature intermittent, large-amplitude fluctuations which are attributed to the radial outwards propagation of plasma blobs through this volume. We introduce a stochastic model which describes scrape-off layer time series by superposing uncorrelated pulses with variable amplitude. The resulting time series is Gamma distributed where the lowest order statistical moments are given by the pulse parameters. The power spectral density is governed by the pulse shape - for a double exponential pulse shape presents the power spectral density a flat region for low frequencies and a steep power law scaling for high frequencies. Predictions from this model are compared to fluctuation measurements of electron density, temperature and plasma potential by mirror Langmuir probes in the SOL during an ohmic L-mode discharge in Alcator C-Mod.