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Experiments for studying the dynamics of solar flux loops
 

Initial experiments have been carried out in Argon, Helium and Hydrogen plasmas in Magnetic Reconnection Experiment (MRX) to study the detailed dynamic evolution of flux ropes relevant to the solar atmosphere. The figure below shows the experimental setup. A plasma arc is initiated and maintained by two electrodes. The electrodes are connected to a pulsed power supply. The plasma arc can be maintained at the desired height for much longer time than the Alfven time (0.5-1 millisecond >100 τA), as is the case for a solar flare. Internal probe arrays are used to measure the magnetic profile of the flare. The q value, which describes the rotational transform of field lines, is the key for characterizing the global stability. When the external toroidal ?eld is high (with q > 1) the flux loop immediately reaches a stable equilibrium and does not move around. When the toroidal field is low (with q < 1) the flux loops becomes unstable and moves around violently. The initial data have shown that line-tying plays an important role in the cathode side of the plasma arc as well as in the discharge evolution. The results from these experiments will be digested in the context of Coronal Mass Ejection (CME) dynamics, which we believe will make a valuable contribution to understanding eruptions on the Sun; this study will contribute to the interpretation of data from Hinode, STEREO, and the upcoming SDO mission by providing "ground truth" for the many theoretical and modeling groups working on simulations of the twisted flux rope model.

 

MRX Vessel

 

MRX vacuum vessel for the initial experiments. A plasma arc (dark red) is initiated from and maintained by two electrodes which are connected to a pulsed power supply (not shown). Various coils provide the necessary vacuum magnetic field for the experiments: current flowing along the 8 toroidal field coils (green) provides the toroidal magnetic field, Bt, which is aligned parallel to the axis of the plasma arc; one pair of DC coils external to the vacuum chamber (big gray circles) provides a steady component of the equilibrium field (BE). The current flowing in the plasma arc provides the poloidal field component (Bp), twisting the field lines. Also shown is the 2-D magnetic probe array.

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