Author:

Abstract:

Magnetic field lines in MHD plasmas constrain the plasma fluid motions. Magnetic fields in the MHD plasma have corresponding image (ie source) currents, and the currents plus their magnetic fields form flux ropes. The flux rope is the simplest macroscopic representation of field lines that includes the particle gyro orbit and dynamical structure. Understanding the dynamics of these MHD flux rope "building blocks" and their mutual interactions offers the key to many important solar, magnetosphere and astrophysical phenomena, including magnetic reconnection and turbulence. An experimental laboratory model using the Reconnection Scaling Experiment (RSX) can create 1, 2 or more long, thin flux ropes, with current embedded parallel to an externally furnished magnetic guide field. These current channels mutually attract via strong, ideal MHD JxB forces. We show experimental data that illustrate unexpected dynamics of the flux ropes in three dimensions. Surprises that undoubtedly affect the statistics of the ensemble of field lines include bouncing flux ropes, orbits that appear to be governed by Keplerian central forces. In addition we observe the commonly expected merging - reconnection of flux ropes which in 2D corresponds to the island coalescence instability. All of these effects are driven by a 3D plasma instability (the kink in our case) that can for example initiate reconnection, with subsequent saturation or stagnation related to the fluid-like forces, mass, flows, and dynamics of the participating plasma and its current system.