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Annales Geophysicae 19, 10/12 (2001) 1411-1420

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. Möbius 1, H. Kucharek 2, C. Mouikis 1, E. Georgescu 2, L. M. Kistler 1, M. A. Popecki 1, M. Scholer 2, J. M. Bosqued 3, H. Rème 3, C. W. Carlson 4, B. Klecker 2, A. Korth 5, G. K. Parks 4, J. C. Sauvaud 3, H. Balsiger 6, M.-B. Bavassano-Cattaneo 7, I. Dandouras 3, A. M. Dilellis 7, L. Eliasson 8, V. Formisano 7, T. Horbury 9, W. Lennartsson 10, R. Lundin 8, M. Mccarthy 11, J. P. McFadden 4, G. Paschmann 2

(2001)

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.

1:	Institute for Study of Earth, Oceans and Space
	University of New Hampshire
2:	Max-Planck-Institut für extraterrestrische Physik
	Max-Planck-Institut für extraterrestrische Physik
3:	Centre d'étude spatiale des rayonnements (CESR)
	CNRS : UMR5187 – Observatoire Midi-Pyrénées – INSU – Université Paul Sabatier [UPS] - Toulouse III
4:	Space Sciences Laboratory (SSL)
	Space Sciences Laboratory (SSL)
5:	Max-Planck-Institut für Aeronomie
	Max-Planck-Institut für Aeronomie
6:	Physikalisches Institut der Universität Bern
	Physikalisches Institut der Universität Bern
7:	Interplanetary Space Physics Institute (IFSI) (IFSI-INAF)
	Interplanetary Space Physics Institute
8:	Institut for Rømdfysik
	Institut for Rømdfysik
9:	Imperial College
	Imperial College
10:	Lockheed-Martin Palo Alto Research Laboratory
	Lockheed-Martin Palo Alto Research Laboratory
11:	Space Program
	Space Program

Subject

:

Sciences of the Universe/Ocean, Atmosphere Sciences of the Universe/Earth Sciences

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Submitted on: Monday, 1 January 2001 08:00:00

Updated on: Friday, 10 October 2008 14:50:22