HR: 16:30h
AN: SH32D-03    [PDF]
TI: Observations of Two-Component Upstream Ions by Cluster
AU: * Wilber, M
EM: wilber@ssl.berkeley.edu
AF: Space Sciences Laboratory, Box 7450 University of California, Berkeley, CA 94720 United States
AU: Meziane, K
EM: karim@unb.ca
AF: University of New Brunswick, Physics Department, Fredericton, NB E3B 5A3 Canada
AU: Parks, G K
EM: parks@ssl.berkeley.edu
AF: Space Sciences Laboratory, Box 7450 University of California, Berkeley, CA 94720 United States
AU: Hull, A J
EM: ahull@ssl.berkeley.edu
AF: Space Sciences Laboratory, Box 7450 University of California, Berkeley, CA 94720 United States
AU: Reme, H
EM: Henri.Reme@cesr.fr
AF: CESR/CNRS, 9 Avenue du Colonel Roche, B.P. 4346 Cedex 4, Toulouse, 31028 France
AU: Dandouras, I
EM: Iannis.Dandouras@cesr.fr
AF: CESR/CNRS, 9 Avenue du Colonel Roche, B.P. 4346 Cedex 4, Toulouse, 31028 France
AU: Mazelle, C
EM: mazelle@cesr.fr
AF: CESR/CNRS, 9 Avenue du Colonel Roche, B.P. 4346 Cedex 4, Toulouse, 31028 France
AU: Kistler, L M
EM: lynn.kistler@unh.edu
AF: Space Science Center, University of New Hampshire, Durham, NH 03824 United States
AU: Lucek, E
EM: e.lucek@imperial.ac.uk
AF: The Blackett Laboratory, Imperial College, Prince Consort Rd., London, SW7 2BZ United Kingdom
AU: Bosqued, J
EM: Jean-Michel.Bosqued@cesr.fr
AF: CESR/CNRS, 9 Avenue du Colonel Roche, B.P. 4346 Cedex 4, Toulouse, 31028 France
AU: Korth, A
EM: korth@linmpi.mpg.de
AF: Max-Planck-Institut fur Aeronomie, Max-Planck-Str. 2, Katlenburg-Lindau, 37191 Germany
AU: Bavassano-Cattaneo, M B
EM: bice@ifsi.rm.cnr.it
AF: IFSI-CNR, Area di Ricerca di Toz Vergata Via del Fosso del Cavaliere, Roma, 00133 Italy
AU: Lundin, R
EM: rickard.kundin@irf.se
AF: Swedish Institute of Space Physics, Box 812, Kiruna, 98128 Sweden
AB: We report on observations by Cluster of two simultaneous upstream ion populations in oblique to quasi-parallel geometries, while the spacecraft were near (probably $\leq 1$ Re) the bow shock. One stable ~1--4 keV component can be seen to gyrate with small pitch angles, while a second, previously un-reported, 10--20 keV population gyrates with much larger pitch angles. A representative case on 23 April 2001 showed a 3--4 keV field-aligned beam change to a 1 keV population having field-aligned velocities 40% lower and pitch angles of $\sim~15^{\circ}$. This change occurred as the IMF rotated 10 degrees, producing a transition from an estimated shock geometry of $\theta_{Bn} \sim~45^{\circ}$ degrees to $\theta_{Bn} \sim~ 36^{\circ}$. The IMF also changed from being very steady to supporting large ULF waves. As the wave amplitudes reached peak values, a 20 keV gyrating component emerged, and this was observed to have pitch-angles of 60--80 degrees, and a narrow spread in gyrophase. After briefly presenting these and similar observations, we will discuss possible sources/mechanisms leading to the emergence of the simultaneous energetic component.
UR: http://sprg.ssl.berkeley.edu/~wilber/AGUFallMeeting2003/
DE: 2118 Energetic particles, solar
DE: 2154 Planetary bow shocks
SC: SPA - Solar and Heliospheric Physics [SH]
MN: 2003 Fall Meeting