Rogue w aves in super∞uid helium

Rogue waves have been observed in super∞uid helium. The experimen- tal system consists of high intensity second sound (temperature-entropy) waves within a resonant cavity. Under steady state conditions, with a constant oscilla- tory driving force at the resonant frequency, the waves are turbulent and there are ∞uxes of energy towards both high and low frequencies. Rogue waves appear under the nonequilibrium conditions that prevail shortly after the drive has been switched on, prior to establishment of the steady state. The experiment is de- scribed brie∞y, relevant results are presented and discussed theoretically in terms of nonlinear wave interactions, and possible connections to rogue waves on the ocean are considered.