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Annales Geophysicae An interactive open-access journal of the European Geosciences Union
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Volume 19, issue 10/12
Ann. Geophys., 19, 1411–1420, 2001
© Author(s) 2001. This work is distributed under
the Creative Commons Attribution 3.0 License.

Special issue: CLUSTER

Ann. Geophys., 19, 1411–1420, 2001
© Author(s) 2001. This work is distributed under
the Creative Commons Attribution 3.0 License.

  30 Sep 2001

30 Sep 2001

Observations of the spatial and temporal structure of field-aligned beam and gyrating ring distributions at the quasi-perpendicular bow shock with Cluster CIS

E. Möbius1, H. Kucharek2, C. Mouikis1, E. Georgescu2, L. M. Kistler1, M. A. Popecki1, M. Scholer2, J. M. Bosqued3, H. Rème3, C. W. Carlson5, B. Klecker2, A. Korth6, G. K. Parks5, J. C. Sauvaud3, H. Balsiger4, M.-B. Bavassano-Cattaneo8, I. Dandouras3, A. M. DiLellis8, L. Eliasson9, V. Formisano8, T. Horbury10, W. Lennartsson7, R. Lundin9, M. McCarthy11, J. P. McFadden5, and G. Paschmann2 E. Möbius et al.
  • 1Dept. of Physics and Institute for the Study of Earth, Oceans and Space, University of New Hampshire, Durham, NH, USA
  • 2Max-Planck-Institut für extraterrestrische Physik, Garching, Germany
  • 3Centre d’Etude Spatiale et Rayonnement, Toulouse, France
  • 4Physikalisches Institut der Universität Bern, Switzerland
  • 5Space Sciences Laboratory, University of California, Berkeley, USA
  • 6Max-Planck-Institut für Aeronomie, Katlenburg-Lindau, Germany
  • 7Lockheed-Martin Palo Alto Research Laboratory, Palo Alto, USA
  • 8Istituto di Fisica dello Spazio Interplanetario, Rome, Italy
  • 9Institut for Rømdfysik, Kiruna, Sweden
  • 10Imperial College, London, UK
  • 11Space Program, University of Washington, USA

Abstract. During the early orbit phase, the Cluster spacecraft have repeatedly crossed the perpendicular Earth’s bow shock and provided the first multi-spacecraft measurements. We have analyzed data from the Cluster Ion Spectrometry experiment (CIS), which observes the 3D-ion distribution function of the major species in the energy range of 5 eV to 40 keV with a 4 s resolution. Beams of reflected ions were observed simultaneously at all spacecraft locations and could be tracked from upstream to the shock itself. They were found to originate from the same distribution of ions that constitutes the reflected gyrating ions, which form a ring distribution in the velocity space immediately upstream and downstream of the shock. This observation suggests a common origin of ring and beam populations at quasi-perpendicular shocks in the form of specular reflection and immediate pitch angle scattering. Generally, the spatial evolution across the shock is very similar on all spacecraft, but phased in time according to their relative location. However, a distinct temporal structure of the ion fluxes in the field-aligned beam is observed that varies simultaneously on all spacecraft. This is likely to reflect the variations in the reflection and scattering efficiencies.

Key words. Interplanetary physics (planetary bow shocks; energetic particles; instruments and techniques)

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