Multi-scale observations of magnetic reconnection: Cluster and MMS measurements of the reconnecting magnetopause at the subsolar region and dusk sector

Magnetic reconnection is a fundamental plasma process that couples the shocked solar wind to the Earth's magnetosphere, allowing the interchange of energy and mass. The X line of magnetic reconnection lies along the magnetopause but its extent and orientation are only partially understood, despite its importance for understanding global solar wind - magnetosphere coupling. We have identified a series of conjunctions between the MMS and Cluster missions where they crossed simultaneously the magnetopause at locations separated by several Earth radii: MMS spacecraft were in the subsolar region while Cluster were in the dusk flank. We identify signatures of reconnection at both spacecraft, allowing us to draw new conclusions about the extent, orientation and time variations of the X line along the magnetopause.