PROBING MACROSCOPIC DYNAMICS OF THE VORTEX TANGLE IN HE-II WITH SMALLAMPLITUDE 2ND SOUND-WAVES

The different interpretations of the Vinen equation lead to different hydrodynamic equations of He II. In particular the mutual friction for ce includes an additional term which can be either positive or negativ e, depending on the detailed interpretation of the vortex tangle dynam ics. A specially designed experiment showed the reduction of the dampi ng of small amplitude second sound pulses propagating through a dense strongly nonequilibrium vortex tangle. Analyzing the observed results we can conclude that the form of the Vinen vortex line density evoluti on equation is correct, but the processes involved correspond better t o Schwarz's microscopic model.