HR: 11:20h
AN: SM52A-05    [Abstracts]
TI: Cluster Cusp Crossing on 18 April 2002
AU: Alleyne, H
SM52A-05 AF: University of Sheffield, Control Engineering, Mappin Street, Sheffield, S1 3JD United Kingdom
AU: * Nanan, B
EM: B.Nanan@sheffield.ac.uk
AF: University of Sheffield, Control Engineering, Mappin Street, Sheffield, S1 3JD United Kingdom
AU: Walker, S
SM52A-05 AF: University of Sheffield, Control Engineering, Mappin Street, Sheffield, S1 3JD United Kingdom
AU: Decreau, P
SM52A-05 AF: LPCE, LPCE/CNRS, Orleans Cedex 2, F-45071 France
AU: Andre, M
SM52A-05 AF: SISP, Swedish Institute of Space Physics, Uppsala, S-75121 Sweden
AU: Balogh, A
SM52A-05 AF: Blackett Laboratory, Imperial College, London, SW7 2BZ United Kingdom
AU: Fazakerley, A
SM52A-05 AF: Mullard Space Science Lab., University college, Surrey, RH5 6KT United Kingdom
AU: Reme, H
SM52A-05 AF: CESR, CESR, Toulouse 04, F-31028 France
AU: Fraenz, M
SM52A-05 AF: MPI, Max-Plank-Str.2, Lindau, 37191 Germany
AU: Cornilleau, N
SM52A-05 AF: CETP, CETP/CNRS, Velizy, F-78140 France
AU: Gurnett, D
SM52A-05 AF: University of Iowa, Iowa, Iowa, Iowa United States
AB: On 18 April 2002 the Cluster spacecraft crossed through a cusp-like region in the northern high altitude magnetosphere during 16:25-17:55 UT when the spacecraft co-ordinates ranged from X = 6.67 to 8.02 Re, Y = -2.5 to -3.98 Re and Z = 8.22 to 8.19 Re. The cusp crossing occurred when a moderate geomagnetic storm was in progress, solar wind dynamic pressure was rather low, IMF Bz was suitable (southward) for magnetic reconnection in the dayside magnetopause, and solar wind azimuthal flow changed from about 5 km s^-1 to -45 km s^-1 at 17:05 UT (shifted by 50 min) and remained at this level even after the cusp crossing. The study of the FGM, CIS, PEACE and WHISPER data from all four spacecrafts reveal that the cusp region is structured with three anti-sunward ion flow events. The events are found to have durations of ~ 1.5, 17.5 and 19.0 min, with bulk flow roughly parallel to the magnetopause toward north. The ion and electron densities in the events are up to eight times greater and those outside the events are up to four times greater compared to the densities outside the cusp. The sharp inward boundaries of the ion flow events are found to cross the four spacecrafts in one time sequence, and the outward boundaries of the events are found to cross the spacecrafts in the reverse time sequence. The observations seem to suggest that the structured cusp is a temporal feature rather than a spatial effect. All features of the observations can be understood if the three ion flow events occurred in sequence (probably due to time-dependent reconnection) while the spacecrafts crossed through the cusp region. Zong et al. [2004] presented the RAPID data during this cusp event and discussed major part of it as a triple cusp.
DE: 2706 Cusp
DE: 2723 Magnetic reconnection (7526, 7835)
DE: 2731 Magnetosphere: outer
DE: 2784 Solar wind/magnetosphere interactions
DE: 2794 Instruments and techniques
SC: SPA-Magnetospheric Physics [SM]
MN: Fall Meeting 2005