  This study presents three-dimensional (3D) resistive Hall-magnetohydrodynamic
simulations of the Kelvin-Helmholtz instability (KHI) dynamics at Earth's
magnetospheric flanks during northward interplanetary magnetic field periods.
By comparing two simulations with and without initial magnetic shear, we
analyze the impact of distinct magnetic field orientations on plasma dynamics
and magnetic reconnection events taking into account 3D mechanisms, such as KHI
high latitude stabilization. The identical nature of the simulations, except
for the presence/absence of an initial magnetic shear, enables, for the first
time, a complete and coherent comparative analysis of the latitudinal
distribution of KH vortices, current sheets, reconnection events, and the
evolution of the mixing layer. In one configuration, a uniform magnetic field
leads to double mid-latitude reconnection (MLR), while in the other, magnetic
shear induces both type I vortex-induced reconnection (VIR) and MLR. Notably,
the type I VIR observed in this second scenario results from the combined
action of line advection and vortex-induced current sheet pinching (the classic
mechanism driving two-dimensional type I VIR). Of particular importance is our
quantification of newly closed field lines that experienced double
reconnection, ultimately becoming embedded in solar wind plasma at low
latitudes while remaining connected to magnetospheric plasma at high latitudes.
The varying abundance of such lines in the two simulations holds implications
for plasma transport at the magnetopause.
