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P: Fachverband Plasmaphysik
P 22: Poster: Sonstiges
P 22.3: Poster
Thursday, March 15, 2012, 16:30–19:00, Poster.III
Expansion Velocity of Arch-shaped Magnetic Flux Tubes — •Jan Tenfelde1, Jürgen Dreher2, Philipp Kempkes3, Felix Mackel1, Sascha Ridder1, Henning Soltwisch1, Richard D. Sydora4, and Thomas Tacke2 — 1Institut für Experimentalphysik V - AG Laser- und Plasmaphysik, Ruhr-Universität Bochum — 2Institut für Theoretische Physik I, Ruhr-Universität Bochum — 3Ernst-Moritz-Arndt-Universität Greifswald, MPI for Plasma Physics, Greifswald — 4University of Alberta, Edmonton, Canada
The arch-shaped flux tubes generated in the FlareLab discharge show constant diameter and apex expansion velocities. The expansion at constant rate is unexpected, as the steeply rising discharge current should cause a continual increase of the hoop force and lead to an accelerated expansion of the plasma arch. This is observed for a wide range of operational parameters and already develops in early stages of the discharge evolution.
Time-dependent numerical MHD-simulations model the flux tube expansion using an approximate arch equilibrium. In the kink-unstable regime, an inward modulation of the apex of the plasma arch is observed, which could lead to a reduction of the observed velocity. The predicted evolution of the flux tube as obtained from the simulations is then compared to measured characteristics from the laboratory experiment.