Observation and Reconstruction of Electron Vortex in Reconnection Outflow

On 27 January 2017, Magnetospheric Multi-Scale observed a series of electron vortexes, which are driven by the electron Kelvin-Helmholtz (K-H) instability in the reconnection outflow at terrestrial magnetopause. We find the electron vorticity can reach above 200 s⁻¹ inside the vortexes, which is comparable to the strong vorticity events in the electron diffusion region. Using the First-Order Taylor Expansion for Velocity field method, we further reconstruct the 3D topology of two electron vortexes and find one vortex is converging while another vortex is diverging. Interestingly, enhancement of electron temperature was observed in the diverging vortex but not in the converging vortex, indicating electron dynamics is related to the vortex topology. Our study suggests that electron K-H vortexes formed by the intense electron shear flow in the reconnection outflow have different types of topologies and will help us better understand the reconnection picture at the terrestrial magnetopause.