HR: 1340h
AN: SH33A-1199    [Abstracts]
TI: Relaxation of flux ropes and magnetic reconnection in the Reconnection Scaling Experiment at LANL
AU: Furno, I
EM: furno@lanl.gov
AF: P-24 Division, Los Alamos National Laboratory, Los Alamos, NM 87544 United States
AU: Intrator, T
EM: intrator@lanl.gov
AF: P-24 Division, Los Alamos National Laboratory, Los Alamos, NM 87544 United States
AU: Hemsing, E
EM: ehemsing@lanl.gov
AF: P-24 Division, Los Alamos National Laboratory, Los Alamos, NM 87544 United States
AU: Hsu, S
EM: scotthsu@lanl.gov
AF: P-24 Division, Los Alamos National Laboratory, Los Alamos, NM 87544 United States
AU: * Lapenta, G
EM: lapenta@lanl.gov
AF: P-24 Division, Los Alamos National Laboratory, Los Alamos, NM 87544 United States
AU: Abbate, S
EM: abbate@lanl.gov
AF: P-24 Division, Los Alamos National Laboratory, Los Alamos, NM 87544 United States
AB: Magnetic reconnection and plasma relaxation are studied in the Reconnection Scaling Experiment (RSX) with current carrying plasma columns (magnetic flux ropes). Using plasma guns, multiple flux ropes ($B_\theta \leq 100$ Gauss, $L=90 $ cm, $r\leq3$ cm) are generated in a three-dimensional (3D) cylindrical geometry and are observed to evolve dynamically during the injection of magnetic helicity. Detailed evolution of electron density, temperature, plasma potential and magnetic field structures is reconstructed experimentally and visible light emission is captured with a fast-gated, intensified CCD camera to provide insight into the global flux rope dynamics. Experiments with two flux ropes in collisional plasmas and in a strong axial guide field ($B_z / B_\theta > 10$) suggest that magnetic reconnection plays an important role in the initial stages of flux rope evolution. During the early stages of the applied current drive ($t\leq 20 $ $\tau_{Alfv\acute{e}n}$), the flux ropes are observed to twist, partially coalesce and form a thin current sheet with a scale size comparable to that of the ion sound gyro-radius. Here, non-ideal terms in a generalized Ohm's Law appear to play a significant role in the 3D reconnection process as shown by the presence of a strong axial pressure gradient in the current sheet. In addition, a density perturbation with a structure characteristic of a kinetic Alfv\'{e}n wave is observed to propagate axially in the current layer, anti-parallel to the induced sheet current. Later in the evolution, when a sufficient amount of helicity is injected into the system, a critical threshold for the kink instability is exceeded and the helical twisting of each individual flux rope can dominate the dynamics of the system. This may prevent the complete coalescence of the flux ropes.
DE: 7827 Kinetic and MHD theory
DE: 7835 Magnetic reconnection
DE: 2752 MHD waves and instabilities
DE: 0654 Plasmas
SC: SPA-Solar and Heliospheric Physics [SH]
MN: 2004 AGU Fall Meeting