Multi-scale processes of dayside magnetopause reconnection: a coordinated observation

We report an observation on 21 December 2019 when the Magnetospheric Multiscale (MMS) spacecraft encountered secondary magnetic reconnection located between two primary X-lines, at the low latitude magnetopause. Solar wind conditions provided by the Advanced Composition Explorer (ACE) spacecraft show that several, short IMF-B_z reversals occurred in this period. This caused a number of foreshock transients and magnetosheath perturbations, which were simultaneously observed by the Time History of Events and Macroscale Interactions during Substorms (THEMIS) spacecraft D and A. Under such influence, several small-scale flux transfer events (FTEs) with different sizes and axis orientations were observed by MMS, adjacent to an apparent X-line crossing. Meanwhile two larger-scale FTE signatures were also later observed afterwards by both Cluster 1 and 3 (located at high northern latitudes magnetopause), both with similar time delays of ~4 min from MMS FTEs. Notably, electron jets with different V_L and V_N were observed by MMS 1-3 adjacent to the flux ropes. We used multi-spacecraft Grad-Shafranov (GS) reconstruction to study the spatial structures of the flux ropes, also the relations to the electron jets. Our results improve our understanding of how solar wind influence the multi-scale processes of magnetopause reconnection, through foreshock transients and magnetosheath disturbance.