© Author(s) 2011. This work is distributed
under the Creative Commons Attribution 3.0 License.
Suprathermal electron acceleration during reconnection onset in the magnetotail
1Swedish Institute of Space Physics, Uppsala, P.O. Box 537, 751 21 Uppsala, Sweden
2Laboratoire de Physique des Plasmas, Laboratoire de Physique des Plasmas, CNRS-Ecole Polytechnique-UPMC, Observatoire de Saint-Maur, 4 avenue de Neptune, 94107 Saint-Maur-des-Fossés, France
3Space Research Institute, Austrian Academy of Sciences, Graz, Austria
Abstract. We study one event of reconnection onset associated to a small substorm on 27 September 2006 by using Cluster observations at inter-spacecraft separation of about 10 000 km. We focus on the acceleration of suprathermal electrons during different stages of reconnection. We show that several distinct stages of acceleration occur: (1) moderate acceleration during reconnection of pre-existing plasma sheet flux tubes, (2) stronger acceleration during reconnection of lobe flux tubes, (3) production of the most energetic electrons within dipolarization fronts (magnetic pile-up regions). The strongest acceleration is reached at the location of Bz maxima inside the magnetic pile-up region where the reconnection jet stops. Very strong localized dawn-dusk electric field are observed within the magnetic pile-up regions and are associated to most of the magnetic flux transport.