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JOURNAL OF GEOPHYSICAL RESEARCH, VOL. 113, A07S30, doi:10.1029/2007JA012770, 2008

Multispacecraft observation of electron beam in reconnection region

A. Åsnes

ESA/ESTEC, Nordwijk, Netherlands


M. G. G. T. Taylor

ESA/ESTEC, Nordwijk, Netherlands


A. L. Borg

Norwegian Defence Research Establishment, Kjeller, Norway


B. Lavraud

Space Science and Applications, Los Alamos National Laboratory, Los Alamos, New Mexico, USA


R. W. H. Friedel

Space Science and Applications, Los Alamos National Laboratory, Los Alamos, New Mexico, USA


C. P. Escoubet

ESA/ESTEC, Nordwijk, Netherlands


H. Laakso

ESA/ESTEC, Nordwijk, Netherlands


P. Daly

Max Planck Institute for Solar System Research, Katlenburg-Lindau, Germany


A. N. Fazakerley

Mullard Space Science Laboratory, Dorking, UK


Abstract

On the 18th of August 2002, during a crossing of the near-Earth plasma sheet Cluster observed an ion flow burst, caused by a near-Earth reconnection event. Cluster observed a tailward bulk flow which reverse to earthward flow, indicating a close passage of the diffusion region. We show that reversals in B Z and B Y are consistent with reconnection. During the event, a short duration burst of electrons in the range of a few keV up to more than 100 keV are observed streaming away from the reconnection region. The accelerated electrons were aligned with the magnetic field, streaming tailward, and were observed simultaneously by all four spacecraft located on both the northern and southern side of the current sheet. The four Cluster spacecraft, separated by ∼3700 km, observe the electrons for a time period of ∼60 s, indicating the burst to be a temporal rather than localized feature. A second burst of tailward accelerated electrons observed for ∼40 s was observed by Cluster 1 and 2 upon entering the earthward outflow region. The second beam thus appear to be directed toward the X-line. The flux levels of the energetic electron bursts exceed those of the ambient plasma sheet by a factor 2–4. In general, the highest energetic electron fluxes during this event were observed in the earthward outflow region. Observations indicate that reconnection operates on closed plasma sheet field lines in this event and does not reach lobe field lines.

Received 27 August 2007; accepted 8 January 2008; published 10 May 2008.

Keywords: reconnection; acceleration; electrons.

Index Terms: 2723 Magnetospheric Physics: Magnetic reconnection (7526, 7835); 2764 Magnetospheric Physics: Plasma sheet; 2744 Magnetospheric Physics: Magnetotail; 2740 Magnetospheric Physics: Magnetospheric configuration and dynamics; 2712 Magnetospheric Physics: Electric fields (2411).

Subscriber Access to Full Article (Nonsubscribers may purchase for $9.00, Includes print PDF, file size: 5544516 bytes)

Citation: Åsnes, A., M. G. G. T. Taylor, A. L. Borg, B. Lavraud, R. W. H. Friedel, C. P. Escoubet, H. Laakso, P. Daly, and A. N. Fazakerley (2008), Multispacecraft observation of electron beam in reconnection region, J. Geophys. Res., 113, A07S30, doi:10.1029/2007JA012770.