Evidence for an extended reconnection line at the dayside magnetopause

We report in-situ detection by two spacecraft of oppositely directed jets of plasma emanating from a magnetic reconnection site at the Earth’s dayside magnetopause, confirming a key element inherent in all reconnection scenarios. The dual-spacecraft (Equator-S and Geotail) observations at the flank magnetopause, together with SuperDARNHalley radar observations of the subsolar cusp region, reveal the presence of a rather stable and extended reconnection line which lies along the equatorial magnetopause. These observations were made under persistent southward interplanetary magnetic field (IMF) conditions, implying that under these conditions the reconnection sites are determined by the large-scale interactions between the solar wind magnetic field and the dayside magnetosphere, rather than by local conditions at the magnetopause. Control by local conditionswould result in patchy reconnection, distributed in a less well-organized fashion over the magnetopause surface.