Methods for Observation of Turbulence Interaction in case of GeodesicAcoustic ModesA. Krämer-Flecken1, D. Prisiazhniuk2;3, P. Manz2;31Institut für Energie- und Klimaforschung / Plasmaphysik, Forschungszentrum Jülich GmbH,D–52425 Jülich, Germany2Max Planck Institut für Plasmaphysik, D–85748 Garching, Germany3Physic-Department E28, Technische Universität München, 85748 Garching, GermanyBeside the observation of turbulence and its characterization, the interaction of small scale tur-bulence structures with mean equilibrium driven flows andEBflows is of major interest tounderstand the energy transfer from the turbulence scale to mesoscales.In the past large efforts are performed to describe interaction of geodesic acoustic modes (GAMs)with ambient turbulence. Due-to nonlinear interaction GAMs modulate the envelope e.g. throughparametric-modulation instability [1]. GAMs are supposed to take the energy from the ambi-ent turbulence and convert it in oscillations of the poloidal velocity. The underlying nonlinearinteraction is mostly studied with bicoherence analysis. But also auto- and cross-correlationtechniques are used to show that the mean flow is modulated by oscillations at the GAM fre-quency. This technique is quite difficult and needs a high sampling frequency with respect tothe GAM frequency.A much more sensitive and reliable technique is the envelope method which monitors the os-cillation of the ambient turbulence by the GAM. In this presentation this method is investigatedespecially for the use in correlation reflectometry which is sensitive to density fluctuations. Ofmajor interest is the question whether this method can be applied for correlation reflectometryinstalled at those poloidal locations where the GAM induced density fluctuations disappear andonly the mean flow is modulated by GAMs. The method is applied and discussed for the cor-relation reflectometry which was installed at TEXTOR and which had antennae arrays on topand low field side. Especially the influence of the filter range will be discussed and the resultingconclusions will be presented.References[1] Y. Nagashima, K. Itoh, S-I. Itoh, et al., Plasma Phys. Control. Fusion,49, 2007, 1611-162
