Three-Dimensional Dynamics of Mutually Interacting Flux Ropes in PHASMA*

Interacting flux ropes are commonly observed on the Sun and in the terrestrial magnetosphere and have been recreated successfully in the PHASMA (PHAse Space MApping) facility using pulsed plasma guns. In 3D environments, the behavior of flux ropes is more complicated than simply attracting and merging. We report measurements of azimuthal writhing, radial bouncing and reconnection between two flux ropes. Unlike previous experiments, flux ropes in this study are kink-free even when created with currents above the kink threshold, eliminating the role of the kink instability in this study. Kink-free flux ropes are achieved by reducing the current pulse duration to less than the axial Alfvén time. Interestingly, two flux ropes are found to rotate around each other clockwise (in the ion gyromotion direction) or counter-clockwise as the axial current increases or decreases. The magnetic field profile and emission light intensity at different axial planes will be presented for different guide field strengths, axial currents, gas species, and collisionality. We discuss plausible explanations for the rotation of the flux ropes involving the induction from changing currents, boundary conditions, and 3D effects.