Evolution of quantum vortices following reconnection

The dynamics of quantized vortices, after reconnection, is investigated within the localized induction approximation. The numerical simulations of vortex line evolution help to determine the rate of the line-length changes. In the absence of counterflow, the vortex line shortens after each reconnection and line-length reduction is calculated as a function of the friction parameter cr and the reconnection angle phi. In the presence of the counterflow V-ns, however, the vortex line shortens at the beginning, but after some time starts to elongate. The summary line-length change of two vortex lines resulting from the reconnection can be well approximated in the form: Delta S = -at(1/2) + bV(ns)(2)t(3/2), With a > 0, b greater than or equal to 0, at least until Delta S less than or equal to 0. Using this observation, the mechanism of sustaining the quantum turbulence can be explained. After a longer time, reconnection disturbance may initiate a generation of a cascade of vortex loops, so the total length of vortices grows sharply. This shows how quantum turbulence can be generated from a score of remnant vortices. (C) 2000 Editions scientifiques et medicales Elsevier SAS.