Observations of Electron Vorticity and Phase Space Holes in the
Magnetopause Reconnection Separatrix
Abstract
We report Magnetospheric MultiScale (MMS) observations of two electron
vortices with a roughly 10 km or 2-3 electron skin depths cross-section
across the magnetospheric separatrix of a dayside magnetopause
reconnection. The enhanced electron vorticity, which is caused by a
significant velocity shear in the electron flows streaming in opposite
directions along northward-directed magnetic field lines, leads to
perturbations perpendicular to the reconnecting magnetic field on the
order of 1-2 nT. The high electron vorticity periods are also associated
with electron phase space holes having the largest bipolar parallel
electric field amplitudes $\sim$ 25 mV/m observed
across this exhaust. Less intense $\sim$ 10 mV/m
electron phase space holes propagate along a northward magnetic field
away from the X-line within a northward reconnection exhaust. The
electron phase space holes with the largest bipolar parallel electric
fields are observed to propagate toward the X-line within discrete
channels of southward and super-Alfv\’{e}nic 1500 km/s
electron flows in the magnetospheric separatrix layer.