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Ann. Geophys., 26, 1539-1544, 2008
www.ann-geophys.net/26/1539/2008/
© European Geosciences Union 2008
On the edge of the foreshock: model-data comparisons
D. G. Sibeck1, N. Omidi2, I. Dandouras3, and E. Lucek4
1Code 674, NASA/GSFC, Greenbelt, MD, USA
2Solana Scientific, Solana Beach, CA, USA
3CESR, Toulouse, France
4Imperial College, London, UK
Abstract. We present the results of a global hybrid code simulation for the solar
wind-interaction with the Earth's magnetosphere during an interval of steady
radial IMF. The model predicts a foreshock marked by innumerable localized,
correlated, and large amplitude, density and magnetic field strength
variations, depressed velocities, and enhanced temperatures. The foreshock
is bounded by a broad (~0.8 RE) region of enhanced densities,
temperatures, and magnetic field strengths that extends far (~8.6 RE)
upstream from the bow shock. Flow perturbations within the boundary
are directed perpendicular to the boundary, towards the unperturbed solar
wind and away from the foreshock. Cluster observations of the ion foreshock
and pristine solar wind confirm the predictions of the model. The
observations suggest that foreshock cavities, crater-like density and
magnetic field strength structures whose cores are filled with suprathermal
particles, can be interpreted in terms of transient encounters with the
foreshock boundary.
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