Extended magnetic reconnection at the Earth's magnetopause from detection of bi-directional jets

Magnetic reconnection is a process that converts magnetic energy into bi-di rectional plasma jets; it is believed to be the dominant process by which s olar-wind energy enters the Earth's magnetosphere(1,2). This energy is subs equently dissipated by magnetic storms and aurorae(3,4). Previous single-sp acecraft observations(5-7) revealed only single jets at the magnetopause-wh ile the existence of a counter-streaming jet was implicitly assumed, no exp erimental confirmation was available. Here we report in situ two-spacecraft observations of bi-directional jets at the magnetopause, finding evidence for a stable and extended reconnection line; the latter implies substantial entry of the solar wind into the magnetosphere. We conclude that reconnect ion is determined by large-scale interactions between the solar wind and th e magnetosphere, rather than by local conditions at the magnetopause.