Drift-wave observation in a toroidal magnetized plasma and comparison with a modified Hasegawa-Wakatani model

International audienceThis paper presents the results of fluctuation measurements in a toroidal magnetized plasma, using Langmuir probes, and comparisons between the observed frequency modes and a Hasegawa-Wakatani model including curvature, adapted to the specifics of the toroidal device. More precisely, two kinds of signals are detected in the presence of an additional vertical magnetic field in the region of significant density and potential gradients. A high frequency, propagating component, corresponding to dissipative drift-waves in the curved magnetic field, is observed and the frequency and typical wavelengths are found to be in good agreement with the linear Hasegawa-Wakatani model including curvature effects. A second, low frequency component is observed at lower frequencies and is shown to correspond to large scale vertical electrostatic field structures. A significantly high level of cross correlation is observed between these two signals, with an identifiable time delay, which suggests an analogy to the time delayed quasi-periodic dynamics in predator-prey systems, and a similar phenomenon is observed between zonal flows and microturbulence in tokamaks and other magnetised plasma systems