Faraday instability of superfluid surface

What is it about?

It is a well-known fact that standing waves are generated on a free surface of Newtonian fluid when its container is vertically vibrated. This is called Faraday instability and regarded as a model system for the physics of pattern formation and nonlinear dynamics. We observed for the first time that the Faraday waves were parametrically generated on a free surface of superfluid $^4$He. Faraday wave was generated at one half of the vibration frequency above a threshold of vibration amplitude in both the normal fluid and superfluid phases. The difference in the threshold between the superfluid and the normal fluid is explained by a wall damping.

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