Characteristics of Electrostatic Solitary waves near the diffusion region associated with reconnection: Cluster and Geotail observations

We report on recent observations of Electrostatic solitary waves (ESWs) by the Wideband PlasmaWave Receiver of Cluster and the Wave From Captures of Geotail near the diffusion region at both sides of X-line. By carefully checking the data of particle, field and wave, we studied the temporal and spatial evolution of ESWs, their relative locations with reconnection layer and the relationship with the distribution functions of electrons. By comparison with full particle simulations, the consistence and inconsistence of the oberservations with simulations will be shown, and we will discuss the role of ESWs in collisionless reconnection.