Magnetospheric Multiscale observations of magnetic reconnection associated with Kelvin‐Helmholtz waves

Abstract The four Magnetospheric Multiscale (MMS) spacecraft recorded the first direct evidence of reconnection exhausts associated with Kelvin‐Helmholtz (KH) waves at the duskside magnetopause on 8 September 2015 which allows for local mass and energy transport across the flank magnetopause. Pressure anisotropy‐weighted Walén analyses confirmed in‐plane exhausts across 22 of 42 KH‐related trailing magnetopause current sheets (CSs). Twenty‐one jets were observed by all spacecraft, with small variations in ion velocity, along the same sunward or antisunward direction with nearly equal probability. One exhaust was only observed by the MMS‐1,2 pair, while MMS‐3,4 traversed a narrow CS (1.5 ion inertial length) in the vicinity of an electron diffusion region. The exhausts were locally 2‐D planar in nature as MMS‐1,2 observed almost identical signatures separated along the guide‐field. Asymmetric magnetic and electric Hall fields are reported in agreement with a strong guide‐field and a weak plasma density asymmetry across the magnetopause CS.