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P. M. Bellan, J. F. Hansen (Caltech)
Solar prominence eruptions have been simulated in the laboratory using a magnetized plasma gun. Still photographs obtained from two high-speed cameras in a stereographic configuration have been combined to make three-dimensional movies of the evolution of the plasma. The plasmas resemble actual solar prominences, and evolve in a reproducible sequence through three stages. First, initial breakdown forms a main current channel consisting of several filaments. Second, the filaments twist around each other. Third, the entire plasma takes on a helical structure and expands outward. The three-dimensional structure of the plasma has a chirality consistent with the sign of the injected helicity.
Plasma behavior has been investigated using various boundary conditions. Most recently, coils generating a vacuum magnetic field straddling the plasma loop have been constructed. Experiments in this configuration show that the vacuum magnetic field delays the eruption of the prominence, as well as limiting the lateral bulging of the plasma loop.
The arched flux tube has a minor radius of 5-15 mm and spans 12 cm between footpoints. The major radius is initially 6 cm and then increases to several times this value as the simulated prominence erupts. Typical maximum plasma currents are 60 kA and typical magnetic fields are 1-5 kG. The duration of the experiment is about 7 microseconds. The experiment takes place in a 1.4 m diameter, 2 m long vacuum chamber and uses hydrogen gas.
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The author(s) of this abstract have provided an email address for comments about the abstract: pbellan@its.caltech.edu