Dissipation enhancement from a single vortex reconnection in superfluid helium

TL;DR

This study shows that a single vortex reconnection in superfluid helium causes Kelvin waves that directly transfer energy to the normal component, with dissipation scaling universally with the mutual friction parameter.

Contribution

It demonstrates that Kelvin-wave cascade is not the main energy dissipation mechanism at certain mutual friction levels, highlighting direct energy transfer from Kelvin waves to the normal component.

Findings

Energy dissipation scales universally with mutual friction parameter.

Kelvin-wave cascade is not significant for energy dissipation at alpha > 0.001.

Vortex minimum distance scales as sqrt(|t - trec|).

Abstract

We investigate a single vortex reconnection event in superfluid helium at finite temperatures using the vortex filament model. The reconnection induces Kelvin waves which strongly increase energy dissipation. We evaluate the mutual friction dissipation from the reconnection and show that the dissipation power has universal form, which is seen by scaling both time (measured from the reconnection event) and power by the mutual friction parameter alpha. This observation allows us to conclude that the Kelvin-wave cascade is not important in the energy dissipation process within the range alpha > 0.001. Rather, the energy is directly transferred from Kelvin waves to the normal component. Moreover, while the excited Kelvin waves greatly enhance energy dissipation, no similar change is seen in angular momentum from the reconnection event. This result has similarities with recent 3He-B measurements. Our results also confirm another earlier observation that the minimum distance between vortices scales approximately as d ~ sqrt(|t-trec|), both before and after the reconnection event.