Cluster observations of currents in the plasma sheet during reconnection

Abstract

We present Cluster PEACE observations of parallel electron currents near a reversal of accelerated ion flows which indicated that the spacecraft were in the vicinity of an active reconnection X-line (XL). Moments calculated from the PEACE electron spectrometer 3D 4s resolution data are analysed. We surveyed the electron current structure to reveal their dependence on distance from the neutral sheet (NS). The electron density and the magnetic field component parallel to the lobe magnetic field were selected as proxies of the distance to the NS. We found that earthward from the XL the electron parallel current switches direction: tailward closer to the NS and earthward nearer to the lobe. On the interface between the tailward and earthward currents we found a narrow layer of strong earthward current. At the same place the largest transverse magnetic disturbances were detected. The observed current structure is consistent with the collisionless reconnection model. However, tailward of the XL no such structure was evident in the data. Copyright 2005 by the American Geophysical Union.