We present the first results of high energy density laboratory astrophysics
experiments which explore the evolution of collimated outflows and jets driven
by a toroidal magnetic field. The experiments are scalable to astrophysical
flows in that critical dimensionless numbers such as the Mach number, the
plasma beta and the magnetic Reynolds number are all in the astrophysically
appropriate ranges. Our experiments use the MAGPIE pulsed power machine and
allow us to explore the role of magnetic pressure in creating and collimating
the outflow as well as showing the creation of a central jet within the broader
outflow cavity. We show that currents flow along this jet and we observe its
collimation to be enhanced by the additional hoop stresses associated with the
generated toroidal field. Although at later times the jet column is observed to
go unstable, the jet retains its collimation. We also present simulations of
the magnetic jet evolution using our two-dimensional resistive
magneto-hydrodynamic (MHD) laboratory code. We conclude with a discussion of
the astrophysical relevance of the experiments and of the stability properties
of the jet.Comment: Accepted by MNRAS. 17 pages without figures. Full version with
figures can be found at
http://www.pas.rochester.edu/~afrank/labastro/MF230rv.pd
