HR: 1400h
AN: SM33B-01    [Abstracts]
TI: High-energy tail associated with backstreaming ions: A comprehensive study
AU: * Meziane, K
EM: karim@unb.ca
AF: Physics Department, University of New-Brunswick, Fredericton, NB E3B 5A3, Canada
AU: Wilber, M
EM: wilber@ssl.berkeley.edu
AF: Space Sciences Laboratory, University of California, Berkeley, CA 94720, United States
AU: Hamza, A M
EM: ahamza@unb.ca
AF: Physics Department, University of New-Brunswick, Fredericton, NB E3B 5A3, Canada
AU: Mazelle, C
EM: mazelle@cesr.fr
AF: CESR, 9, Avenue du Colonel Roche, Toulouse, 31028, France
AU: Reme, H
EM: reme@cesr.fr
AF: CESR, 9, Avenue du Colonel Roche, Toulouse, 31028, France
AU: Lucek, E A
EM: e.lucek@imperial.ac.uk
AF: Blackett Laboratory, Imperial College, London, SW7 2BW, United Kingdom
AB: Detailed particle distributions of backstreaming ions observed upstream of the Earth's bow shock by the Cluster Spacecraft are examined. A recent study found that the characteristics of both parallel and perpendicular particle distribution function profiles of field-aligned beams (FABs) are geometry-dependent [Meziane et al., 2007]. FABs observed at oblique shocks have reduced particle distribution functions that exhibit high-energy tails, in contrast to FABs observed at quasi-perpendicular shocks. Gyrating ion as well as diffuse ion populations also show evidence of high energy tails in the reduced distributions. Usually, these tails are satisfactorily fit with a stretched exponential function. It is not clear whether the tails associated with the different populations are related. The existence of these high energy tails raise interesting issues regarding their origin and how they fit with our current outstanding of of backstreaming ions. It is now accepted that the probability distribution functions tails are likely to arise from a development of nonlinear coherent structures. We have not found any evidence that these tails grow from upstream electromagnetic fluctuations, therefore favoring their production at the shock.
DE: 2134 Interplanetary magnetic fields
DE: 2154 Planetary bow shocks
DE: 2164 Solar wind plasma
DE: 7845 Particle acceleration
DE: 7851 Shock waves (4455)
SC: SPA-Magnetospheric Physics [SM]
MN: 2007 Joint Assembly