Drift-Kinetic Alfvén Waves Observed near a Reconnection X Line in the Earth’s Magnetopause

We identify drift-kinetic Alfvén waves in the vicinity of a reconnection X line on the Earth's magnetopause. The dispersive properties of these waves have been determined using wavelet interferometric techniques applied to multipoint observations from the Cluster spacecraft. Comparison of the observed wave dispersion with that expected for drift-kinetic Alfvén waves shows close agreement. The waves propagate outwards from the X line suggesting that reconnection is a kinetic Alfvén wave source. Energetic O+ ions observed in these waves indicate that reconnection is a driver of auroral ion outflow.