A three-dimensional magnetohydrodynamical simulation of a heavy superm
agnetosonic magnetized jet has been performed. The jet is precessed at
the origin to excite Kelvin-Helmholtz unstable helical modes. The jet
exhibits an apparent large amplitude helical twist induced by the pre
cession. Twin magnetic filaments accompany an elliptical distortion. T
h magnetic filaments twist through 360 degrees over a length scale abo
ut twice that required for jet helicity induced by precession to twist
through 360 degrees. This organized structure is maintained over cons
iderable distance and is associated with a denser jet core that is sur
rounded by a less dense sheath consisting of slower moving jet fluid a
nd a magnetic field mixed with the external medium.