HR: 0800h
AN: SM11A-0304    [Abstracts]
TI: The Statistics of Foreshock Cavities Results of a Cluster Survey
AU: * Billingham, L
EM: laurence.billingham01@imperial.ac.uk
AF: Space and Atmospheric Physics, Blackett Laboratory, Imperial College London, UK, London, SW7 2BW, United Kingdom
AU: Schwartz, S J
EM: s.schwartz@imperial.ac.uk
AF: Space and Atmospheric Physics, Blackett Laboratory, Imperial College London, UK, London, SW7 2BW, United Kingdom
AU: Sibeck, D G
EM: David.g.Sibeck@nasa.gov
AF: Goddard Space Flight Center, Greenbelt, MD, USA, Greenbelt, MD 20771, United States
AB: Kinetic processes occurring upstream of the terrestrial bow shock can greatly perturb the parameters of the Solar Wind incident on the dayside magnetosphere. Foreshock cavities are believed to form when isolated magnetic field bundles connect to to quasi-parallel bow shock. This allows energetic ions to stream back against the Solar Wind flow excavating depressions in density and magnetic field magnitude. It has been suggested that these foreshock cavities may be the most important source of transient events in the outer dayside magnetosphere and high-latitude ionosphere. We present the results of a survey of foreshock cavities conducted with Cluster II magnetic field, plasma and energetic particle instruments. Cavities were observed at a rate of almost one per day when Cluster was upstream of the bow shock. Statistically, there is no significant difference between the solar wind before and after the cavities: they do occur on isolated bundles of flux. Mapping the observed positions of foreshock cavities against previously reported boundaries of the contiguous foreshock yields a puzzling result.
DE: 6939 Magnetospheric physics (2700)
DE: 7800 SPACE PLASMA PHYSICS
SC: SPA-Magnetospheric Physics [SM]
MN: 2007 Fall Meeting