Observation of the growth of a magnetic vortex in the transition layer
  of a mildly relativistic oblique plasma shock
  A 2D particle simulation models the collision of two electron-ion plasma
clouds along a quasi-parallel magnetic field. The collision speed is 0.9c and
the density ratio 10. A current sheet forms at the front of the dense cloud, in
which the electrons and the magnetic field reach energy equipartition with the
ions. A structure composed of a solenoidal and a toroidal magnetic field grows
in this sheet. It resembles that in the cross-section of the torus of a
force-free spheromak, which may provide the coherent magnetic fields in
gamma-ray burst (GRB) jets needed for their prompt emissions.
