Downward current electron beam observed by Cluster and FAST.
J GEOPHYS RES-SPACE
, Article A06202. 10.1029/2007JA012643.
 We report observations from a conjunction of FAST and Cluster during an interval of downward current at an MLT of 3-4 h on field lines mapping to the PSBL. Both spacecraft see upgoing electrons with an energy of a few hundred eV, suggesting substantial acceleration has occurred below FAST's altitude of 3200 km. At Cluster, isolated bursts of electrons are seen, and modeling indicates that the current mapped from the ionosphere exists as a collection of current filaments at Cluster (4-5 R-E). The current filaments are aligned with the background magnetic field and have a perpendicular scale at Cluster of about 100 km (which maps to 10-20 km in the ionosphere), and is similar to the mapped width observed by FAST. The electron beams are quasi-steady during a Cluster spacecraft transit time of 1 min. The field aligned current densities at FAST and Cluster are of the order of a few mu Ams(-2) and 0.05 mu Am-2, respectively, and j/B is conserved along a current filament.
|Title:||Downward current electron beam observed by Cluster and FAST|
|Keywords:||AURORAL CURRENT REGION, SCALE ULF WAVE, TEMPORAL EVOLUTION, FIELDS, SECTOR, ARCS|
|UCL classification:||UCL > School of BEAMS
UCL > School of BEAMS > Faculty of Maths and Physical Sciences
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