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) , Hans 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)

1 Institute for Study of Earth, Oceans and Space
2 MPE - Max-Planck-Institut für Extraterrestrische Physik
3 CESR - Centre d'étude spatiale des rayonnements
4 SSL - Space Sciences Laboratory [Berkeley]
5 MPI Aeronomie - Max-Planck-Institut für Aeronomie
6 Physikalisches Institut [Bern]
7 IFSI - Istituto di Fisica dello Spazio Interplanetario
8 Institut for Rømdfysik
9 Imperial College London
10 Lockheed-Martin Palo Alto Research Laboratory
11 Space Program

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.

Domaines: Océan, Atmosphère; Sciences de la Terre

E. Möbius, H. Kucharek, C. Mouikis, E. Georgescu, L. M. Kistler, et al.. Observations of the spatial and temporal structure of field-aligned beam and gyrating ring distributions at the quasi-perpendicular bow shock with Cluster CIS. Annales Geophysicae, 2001, 19 (10/12), pp.1411-1420. ⟨hal-00329198⟩