Kiel 2011 – scientific programme
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P: Fachverband Plasmaphysik
P 16: Poster: Niedertemperaturplasmen
P 16.8: Poster
Wednesday, March 30, 2011, 16:30–18:30, Foyer
Kinetic damping of shear Alfvén waves — •Thomas Windisch1, Olaf Grulke1,2, and Thomas Klinger1,2 — 1Max-Planck Institute for Plasma Physics, EURATOM Association, 17491 Greisfwald, Germany — 2Ernst-Moritz Arndt University, 17489 Greifswald, Germany
Alfvén waves are low-frequency (ω≪ ωci) magnetic field perturbations which propagate with the Alfvén velocity va along the ambient magnetic field B0. Besides collisional damping Alfvén waves are damped by kinetic effects, i.e. ion cyclotron and Landau damping, which are important for the heating of the corona and can be utilized as plasma heating mechanism in fusion devices. The cyclotron damping occurs if the wave frequency approaches the resonance at the ion cyclotron frequency ωci. Ions resonate with the wave and are heated by absorbing the wave energy. Wave-particle interaction via Landau damping becomes important if the phase velocity gets close to the electron thermal velocity ve. In the linearly magnetized VINETA experiment Alfvén waves are excited using a Helmholtz antenna. The magnetic field fluctuations are measured with a three-axis miniaturized Ḃ-probe, which allows to characterize the polarization of the wave. A gradient of the ambient magnetic field is used to produce a narrow axial region, in which the frequency of the waves matches the local ion cyclotron frequency. The same mechanism is used to produce an axial decrease of the plasma density, such that va∼ 1/√(n) approaches ve. The experimental findings are compared with estimates of the kinetic dispersion relation.