Exhaust structure of guide-field reconnection under shear flows as seen at the magnetopause flanks

Velocity shear at the magnetopause flanks often supports the development of Kelvin–Helmholtz waves, which can in turn facilitate favourable conditions for local magnetic reconnection. Under these flank conditions, reconnection typically occurs in a configuration characterised by a strong guide field. We extend previous two-dimensional models of shear-flow-modified reconnection to consider the resulting three-dimensional exhaust structure under strong guide-field conditions. This new framework suggests that the exhaust may be bounded by an asymmetric pair of standing shock-like structures, producing a three-dimensional geometry that extends into the out-of-plane (guide-field) direction. Using observations from the Magnetospheric Multiscale (MMS) mission during a dusk-flank magnetopause crossing under northward interplanetary magnetic field conditions, we confirm that reconnection exhausts exhibit these features.