Triple vortex ring structure in superfluid helium II

Superfluids such as helium II consist of two interpenetrating fluids: the n ormal fluid and the superfluid. The helium II vortex ring has generally bee n considered merely as a superfluid object, neglecting any associated motio n of the normal fluid. We report a three-dimensional calculation of the cou pled motion of the normal-fluid and superfluid components, which shows that the helium II vortex ring consists of a superfluid vortex ring accompanied by two coaxial normal-fluid vortex rings of opposite polarity. The three v ortex rings form a coherent, dissipative structure.