Reconnection and energetic particles at the edge of the exterior cuspT. Asikainen and K. MursulaDepartment of Physical Sciences, PoBox 3000, FIN-90014 University of Oulu, Finland
Abstract. In this paper we study flux transfer events (FTE) observed at the post-noon
edge of the exterior cusp region by Cluster satellites. During the outbound
dayside orbit on 2 February 2003, intense bursts of energetic particles were
observed in close conjuction with magnetic field FTE signatures by the RAPID
instrument onboard the Cluster 4. The pitch-angle distribution of the
particles showed that the enhancements consist of particles flowing
antiparallel to the magnetosheath field lines away from the expected
reconnection site to the exterior cusp. At the same time Cluster 3 observed
enhancements of energetic particles deeper in the exterior cusp with a delay
of about 40 s to the Cluster 4 enhancements. The estimated maximum energy
gain per particle by reconnection remains below 1 keV, thus clearly below
the tens to hundreds of keV energy range observed by the RAPID instrument.
These observations support the earlier statistical result of the
magnetospheric origin of energetic particles in the exterior cusp.
Reconnection near the exterior cusp partly releases the particles in the
closed field lines of the adjacent HLPS region into the exterior cusp.
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Citation: Asikainen, T. and Mursula, K.: Reconnection and energetic particles at the edge of the exterior cusp, Ann. Geophys., 24, 1949-1956, 2006. Bibtex EndNote Reference Manager