Greifswald 2024 – wissenschaftliches Programm
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P: Fachverband Plasmaphysik
P 12: Poster II
P 12.9: Poster
Dienstag, 27. Februar 2024, 16:30–18:30, ELP 6: Foyer
Modulational instability in isolated dynamics of Geodesic-Acoustic-Mode packets — •David Korger1,2, Emanuele Poli1, Alessandro Biancalani3, Alberto Bottino1, Omar Maj1, and Juvert Njeck Sama4 — 1Max-Planck-Institut für Plasmaphysik, Garching, 85748, Germany — 2Ulm University, Ulm, 89081, Germany — 3École supérieure d’ingenieurs Léonard-de-Vinci (ESILV), Paris La Défense, F-92916, France — 4Institut Jean Lamour, Université de Lorraine, Nancy, 54011, France
The geodesic-acoustic-mode (GAM) is a plasma oscillation observed in fusion reactors with toroidal geometry and is recognized to be the nonstationary branch of the zonal flows (ZFs). It was recently shown that the dynamics of the isolated, undamped GAM is well described by a (cubic) nonlinear Schrödinger equation (NLSE). This model equation predicts the susceptibility of GAM packets to the modulational instability (MI).
The necessary conditions for this instability are analyzed analytically and numerically using the NLSE model. The predictions of the NLSE are compared to gyrokinetic simulations performed with the global particle-in-cell code ORB5, where the GAM packets are created from initial perturbations of the axisymmetric radial electric field Er. An instability of the GAM packets with respect to modulations is observed, in both cases in which an initial perturbation is imposed and when the instability develops spontaneously. However, significant differences in the dynamics of the small scales are discerned between the NLSE and gyrokinetic simulations.
Keywords: Tokamak; geodesic-acoustic-mode; nonlinear Schrödinger equation; modulational instability; gyrokinetic simulations