Response of a vortex in a magnetized electron plasma to a half-sinusoidal strain pulse

The dynamical response of an initially axisymmetric vortex with uniform vorticity and a large edge vorticity gradient, subjected to a time-dependent sinusoidal strain pulse, is investigated using pure electron plasmas confined in a Penning–Malmberg trap, which serves as an experimental analog for 2D vortex dynamics. The system is examined within the framework of adiabatic theory, where the change in action ΔI quantifies oscillations in aspect ratio and orientation about a strain-dependent elliptical vortex equilibrium. In particular, ΔI is examined for both strong and weak strain, and fast and slow pulses, covering a wide landscape of vortex evolution. At lower values of strain, the vortex closely follows the evolving stable fixed point, and ΔI exhibits periodic breaking modulated by a T−2 envelope. Experimental results show strong agreement with both the pure elliptical model and a simplified analytical solution in this regime. At higher strain, the vortex undergoes phase-space separatrix crossing and significant deformation, deviating from the adiabatic behavior observed at lower amplitudes. In regimes where the vortex elongation exceeds λ≥3, notable discrepancies arise between experimental observations and the model, suggesting the onset of surface perturbations with high wavenumber, an effect not captured by the model.