# Instability of a Vortex Ring due to Toroidal Normal Fluid Flow in Superfluid 4He

## TL;DR

This paper investigates how a toroidal normal fluid flow causes instability in vortex rings within superfluid helium-4, revealing a growth rate independent of vortex ring size and similarities to Kelvin wave instabilities.

## Contribution

It demonstrates that toroidal normal fluid flow induces a vortex ring instability in superfluid helium-4, with growth characteristics akin to Kelvin wave instabilities.

## Key findings

- Instability driven by toroidal normal fluid flow in superfluid helium-4.
- Growth rate of instability is independent of vortex ring radius.
- Qualitative similarity to Donnelly-Glaberson Kelvin wave instability.

## Abstract

Vortex rings self-propelling in superfluid 4He are shown to be driven unstable by a toroidal normal fluid flow. This instability has qualitative similarities with the Donnelly-Glaberson instability of Kelvin waves on a vortex filament driven by the normal fluid flow along the vortex filament. The growth rate of the present instability is found to be independent of the radius of the vortex ring.