Investigation of vortex splitting in non-neutral electron plasmas*

Experiments and particle-in-cell simulations are conducted to study splitting behavior of elliptical, two-dimensional E×B vortices in magnetized non-neutral electron plasmas. The experiments are conducted in a regime where the drift dynamics are isomorphic to the Euler equations describing ideal fluids. High-aspect-ratio elliptical vortices are prepared using strong external E×B strain flows, then the strain is removed and the vortices allowed to relax freely. When the aspect ratio is sufficiently large, the vortices split into multiple pieces due to the Love instability (similar to Kelvin-Helmholtz in elliptical geometry). We show that vortices with realistic smooth edges have aspect ratio splitting thresholds approximately twice as large as that predicted by an idealized model with a discontinuous boundary, possibly due to phase-mixing of the Love modes. This calls into question use of the latter model to describe vortex splitting phenomena in settings such as planetary atmospheres or drift-wave eddies in tokamaks. We also discuss asymmetric splitting events with differently-sized products, and the possible impact of nearby boundaries on the splitting threshold.