Mechanical injection of magnetic helicity during spheromak formation

Experimental evidence is reported for the presence of oppositely rotating plasma cells during spheromak formation. The toroidal rotations are caused by j\ifmmode\times\else\texttimes\fi{}B forces and cause a twisting of axial (i.e., poloidal) magnetic field into the toroidal direction. Calculations of the magnetic helicity input are consistent with measured helicity values. This method of flux conversion can be interpreted as a mechanical source of magnetic helicity injection possibly useful for magnetic confinement of plasmas.