In a large uniform magnetoplasma, time-varying currents are generated with pulsed electrodes, electron beams, and magnetic loop antennas. The magnetic field associated with plasma currents is measured with magnetic probes. Experimental setup and basic parameters. Current pulses propagate dispersively. The topology of short current pulses is that of three-dimensional vortices resembling spheromaks.
Long pulses exhibit the topology of flux-ropes.
The current density is nearly parallel to the magnetic field produced by itself. Nested magnetic surfaces near axis of a current pulse exhibit the topology of a flux rope. Current density surface and field lines near axis of a dc current flux tube also exhibit the topology of a flux rope. Knotted current lines are observed. Helicity decays at the same rate as the energy.