The evolution of laboratory produced magnetic jets is followed numerically through
three-dimensional, nonideal magnetohydrodynamic simulations. The experiments are designed to
study the interaction of a purely toroidal field with an extended plasma background medium. The
system is observed to evolve into a structure consisting of an approximately cylindrical magnetic
cavity with an embedded magnetically confined jet on its axis. The supersonic expansion produces
a shell of swept-up shocked plasma that surrounds and partially confines the magnetic tower.
Currents initially flow along the walls of the cavity and in the jet but the development of
current-driven instabilities leads to the disruption of the jet and a rearrangement of the field and
currents. The top of the cavity breaks up, and a well-collimated, radiatively cooled, “clumpy” jet
emerges from the system.