We performed 2D PIC simulations of Kelvin Helmholtz instability (KHI) with symmetric and asymmetric density and temperature profiles along the flow shear with a northward interplanetary magnetic field. The Magnetic Flux Transport method, field topology and magnetic field minimums are used to identify the reconnection X-lines. We start to observe the reconnection signatures such as magnetic field and flow reversals at the vortex edges in the nonlinear phase of the KHI when the vortices are rolling up. The number of reconnection regions increases at the turbulence phase. The signatures eventually decrease and finally disappear at very turbulent stages of KHI developments. Our results qualitatively agree with MMS observations of reconnection signatures at KHI along the magnetospheric flanks.

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.