Spherically symmetric formation of localized vortex tangle around a heat source in superfluid He4

We study the dynamical process of the vortex tangle development under a spherically symmetric thermal counterflow around a heat source submerged into a bulk superfluid $⁴\mathrm{He}$. We reveal a peculiar vortex dynamics that is unique to this geometry, which is greatly diverse from the vortex dynamics in a homogeneous counterflow. Two types of heater are considered here, namely, a spherical heater with a solid wall and a pointlike heater. In both cases, a spherical vortex tangle is formed surrounding the heater. The mechanism of vortex tangle development in the vicinity of a solid wall is strongly governed by the Donnelly-Glaberson instability; while, far away from the heater or around a point heater, the mechanism is governed by the dynamics of polarized vortex loops in radial counterflow. The decay process of such localized vortex tangles is also investigated and is compared with that of homogeneous vortex tangles.