HR: 0800h
AN: SM21A-0443    [Abstracts]
TI: Cluster Observations of Cusp Population by Solar Wind Compression
AU: Alleyne, H
AF: University of Sheffield, Control and Systems Engineering, Sheffield, S1 3JD United Kingdom
AU: * Balan, N
EM: B.Nanan@sheffield.ac.uk
AF: University of Sheffield, Control and Systems Engineering, Sheffield, S1 3JD United Kingdom
AU: Walker, S
AF: University of Sheffield, Control and Systems Engineering, Sheffield, S1 3JD United Kingdom
AU: Reme, H
AF: CESR, CNRS, Toulouse, Toulouse 04, F-31028 France
AU: Balogh, A
AF: Imperial College, Blackett Laboratory, London, SW7 2BZ United Kingdom
AU: Cornilleau, N
AF: VSQP University, CETP/CNRS, Uelizy, F-78140 France
AB: The Cluster spacecrafts crossed through the southern magnetosheric cusp several times during the geomagnetic storm period 24 October - 03 November 2003. Analysis of the CIS, FGM and STAFF data during these stormtime and previous quiettime cusp crossings provide evidence for the cusp population by solar wind compression during the onset and early main phase of the storms on 24 and 29 October. The crossing on 24 October occurred during the onset of a moderate geomagnetic activity. The prevailing solar wind, as observed by ACE, became strong (pressure over 10 nPa, density up to 80 cm$^{-3}$, speed exceeding 600 km s$^{-1}$) and IMF Bz turned strongly northward at around 15:00 UT. About 30 min later, when Cluster was entering the cusp through the entry layer, the ion density (H$^{+}$ and He$^{++}$) increased suddenly over 50 times and ion velocity turned strongly southward. The cusp crossing on 29th October occurred during the early main phase of a severe geomagnetic storm. The prevailing solar wind became very strong (speed exceeded 1500 km s$^{-1}$; pressure and density not available) and IMF Bx, By and Bz started fluctuating around zero starting at around 05:45 UT. About 20 min later, the Cluster, which was entering the cusp through the entry layer, started detecting over 20 times increase in ion density (H$^{+}$, He$^{++}$ and O$^{+}$), and ion velocity turned strongly southward. These observations of large ion density with strong southward ion flows in the southern magnetospheric cusp, following strong solar wind, indicate cusp population by solar wind compression. The magnetic field components Bx, By and Bz show large fluctuations during both crossings, consistent with the ion velocity fluctuations. Magnetic wave activity also became strong at the time of sudden increase in ion density during both crossings.
DE: 2716 Energetic particles, precipitating
DE: 2724 Magnetopause, cusp, and boundary layers
DE: 2784 Solar wind/magnetosphere interactions
DE: 2788 Storms and substorms
SC: SPA-Magnetospheric Physics [SM]
MN: 2004 AGU Fall Meeting