MMS and Cluster conjugate observation of current sheet disturbances associated with localized fast flows in the near-Earth magnetotail

We report fast flow associated near-Earth magnetotail current sheet disturbances based on conjugate multi-point observations by MMS (Magnetospheric Multiscale) and Cluster probes near the onset of a small substorm around 14 UT, Sep. 8, 2018. Both MMS and Cluster were located about X=17 R_E, separated mainly in the dawn-dusk direction by a distance of about 4 R_E, when they encountered a localized fast flow nearly simultaneously. We analyzed the mesoscale current sheet disturbances based on multi-point data analysis between Cluster and MMS. The analysis has revealed that the current sheet thickened during the passage of the front of the fast flow, in agreement with results from previous statistical studies. The thickness of the current sheet, however, decreased subsequently, before recovering toward the original configuration. MMS observed enhanced off-equatorial field aligned currents exclusively during this thinning of the current sheet. The fine structure of the field-aligned currents consisted of multiple small-scale intense current layers accompanied by enhanced Hall-currents. Based on these mesoscale and small-scale multipoint observations, we infer the 3D current structures around the localized flow and compare with those predicted with those predicted in the reconstructed current wedge. to discuss the context of the flow observation in large-scale magnetotail dynamics.