Experiments on the tearing of a current sheet into a bundle of interacting flux ropes

A narrow ( $\frac{\delta }{L}\approx .05, \delta \simeq 3-10\frac{c}{\omega_{pe} },\delta \mbox{=1cm})$ current sheet is established in a magnetized (B$_{\mathrm{0z}} = $ 200G, He, Len $=$ 17 m, Dia $=$ 60 cm) plasma column. The current sheet is observed to tear into multiple magnetic islands in several Alfv\'{e}n transit times. Volumetric magnetic field data is acquired at 16,500 spatial locations and 16,000 time steps ($\delta $t $=$ .34 $\mu $s). The flux ropes appear as multiple ``O'' and ``X'' points when viewed in a plane perpendicular to the local current but, in fact are three-dimensional. The kink unstable ropes writhe, and twist about each other as the ensemble of ropes spin about the background axial magnetic field. Fast framing camera images ($\tau_{\exp } = 1\mu s$, 34,000 fps) clearly show the motion but differ from shot to shot. The movies are analyzed using correlation techniques. The rope dynamics becomes chaotic therefore correlation techniques using a fixed magnetic probe as well a He II line ($\lambda =303A)$ are used to generate 3D images of the ropes. An emissive probe is used to measure the plasma potential and the total electric field, $\vec{{E}}=-\nabla \phi -\frac{\partial \vec{{A}}}{\partial t}$, and plasma resistivity are evaluated. The perpendicular electric fields are two orders of magnitude larger than the parallel ones. The entropy and complexity of the flux ropes are evaluated.