Pulsating Reconnection in the interaction of Two Magnetic Fux Ropes.

Abstract:

Two flux ropes (dia = 7 cm, ds= 3 cm, L = 10m, I_rope = 300 A/rope) are generated by using a mask in front of a high emissivity cathode (n = 4X10¹² cm³, Te-rope = 8.5 eV) in a background magnetoplasma (He, B_oz= 330 G, n=1.0X10¹² cm³, Te = 4 eV) in the LAPD device at UCLA. The ropes are kink unstable ( I > 250 A) but not violently so. All three components of the magnetic field were measured with small (1 mm dia) 3-axis probes sensitive to and the plasma potential measured with an emissive probe. These were measured at over 42,000 locations in the volume containing the ropes and 7000 time steps (δτ = .33 μs). The total electric field and parallel resistivity as well as the Quasi Seperatrix layer (QSL) were derived from the data. The flux ropes periodically collide as they rotate about when another and kink. Each time this happens a strong QSL (Q<400) forms and the resistivity jumps to over a hundred times the classical value at locations within the QSL and also on the gradient of the rope current. The QSL formation and 3D electric fields are presented as a function of space and time. The reconnection rate is directly evaluated by integrating the electric field along field lines as well as the energy deposition . The data indicate that there is more than one process causing the enhanced resistivity. The reconnection rate cannot be explained by conventional 2D theories.