  The torsional dynamics of a semiflexible polymer with a contour length $L$
larger than its persistence length L_p that is rotated at fixed frequency
omega_0 at one end is studied by scaling arguments and hydrodynamic
simulations. We find a non-equilibrium transition at a critical frequency
omega_*: In the linear regime, omega_0 < omega_*, axial spinning is the
dominant dissipation mode. In the non-linear regime, omega_0 > omega_*, the
twist-dissipation mode involves the continuous creation of plectonemes close to
the driven end and the rotational friction is substantially reduced.
