HR: 15:15h
AN: SM53D-07    [Abstracts]
TI: Auroral nightside downward-current regions: ClusterII observations
AU: * Lynch, K
EM: kristina.lynch@dartmouth.edu
AF: Dartmouth College, 6127 Wilder Lab, Hanover, NH 03755, United States
AU: Fazakerley, A
EM: anf@mssl.ucl.ac.uk
AF: Mullard Space Science Laboratory, Holmbury St Mary, Dorking, Sur RH56NT, United Kingdom
AU: Karlsson, T
EM: tomas.karlsson@ee.kth.se
AF: School of Electrical Engineering, Space and Plasma Physics, Royal Institute of Technology (KTH), Stockholm, SE-100 44, Sweden
AU: Lahiff, A
EM: adl@mssl.ucl.ac.uk
AF: Mullard Space Science Laboratory, Holmbury St Mary, Dorking, Sur RH56NT, United Kingdom
AU: Marklund, G
EM: goran.marklund@ee.kth.se
AF: School of Electrical Engineering, Space and Plasma Physics, Royal Institute of Technology (KTH), Stockholm, SE-100 44, Sweden
AB: The ClusterII spacecraft traverse the nightside auroral zone at 4-6 Re altitudes in February-March of each year. In 2004, their separation was such as to cross the auroral zone with separation times of a few minutes, comparable to the expected timescales of auroral downward current sheet evolution. We present observations from 12 such events from an effort to look for signatures of the temporal evolution of the auroral downward current system. We compare the electron characteristic energy (ratio of energy flux to number flux) and density of the upgoing electron beams as measured by the PEACE instrument, to electric field signatures from EFW including integrated potential, divergent field structures, and ambient density calculated from the spacecraft potential. The events are seen to be localized on or near ambient density gradients. The characteristic energy of the upgoing electrons is inversely proportional to their number density. Characteristic energies of up to a few keV are seen, and these energies typically decrease with time as subsequent spacecraft cross the same event.
DE: 2437 Ionospheric dynamics
DE: 2451 Particle acceleration
DE: 2704 Auroral phenomena (2407)
DE: 2721 Field-aligned currents and current systems (2409)
DE: 2736 Magnetosphere/ionosphere interactions (2431)
SC: SPA-Magnetospheric Physics [SM]
MN: 2007 Fall Meeting