Evidence for an extended reconnection line at the dayside magnetopause

We report in-situ detection by two spacecraft of oppositely directed jets o f plasma emanating from a magnetic reconnection site at the Earth's dayside magnetopause, confirming a key element inherent in all reconnection scenar ios. The dual-spacecraft (Equator-S and Geotail) observations at the flank magnetopause, together with SuperDARN Halley radar observations of the subs olar cusp region, reveal the presence of a rather stable and extended recon nection line which lies along the equatorial magnetopause. These observatio ns were made under persistent southward interplanetary magnetic field (IMF) conditions, implying that under these conditions the reconnection sites ar e determined by the large-scale interactions between the solar wind magneti c field and the dayside magnetosphere, rather than by local conditions at t he magnetopause. Control by local conditions would result in patchy reconne ction, distributed in a less well-organized fashion over the magnetopause s urface.