Electron vorticity at dipolarization fronts

Using magnetospheric multiscale high-resolution measurements, we present the first comprehensive investigation of electron vorticity developing at earthward-propagating dipolarization fronts (DFs). Superposed epoch analysis reveals that electron vorticity increases at and behind the DFs, with its average magnitude slightly larger than lower hybrid frequency, indicating that vorticity is related to Hall dynamics at the DFs. Vorticity at the DFs exhibits clear anisotropy, ω > ωP, where ω, ωP are the components perpendicular and parallel to local magnetic field, respectively. Parametric dependence analysis shows that electron vorticity is well anticorrelated with electron density. We find that in a statistical sense, vorticity-induced magnetic field perturbations are not significant, although in a few cases vorticity can generate intense magnetic field perturbations. This study can improve our current understanding of the DF dynamics.