Articles | Volume 27, issue 8
Ann. Geophys., 27, 3009–3017, 2009

Special issue: Ninth International Conference on Substorms (ICS9)

Ann. Geophys., 27, 3009–3017, 2009

  04 Aug 2009

04 Aug 2009

Observations of plasma vortices in the vicinity of flow-braking: a case study

K. Keika1,2, R. Nakamura1, M. Volwerk1, V. Angelopoulos3, W. Baumjohann1, A. Retinò1, M. Fujimoto4, J. W. Bonnell5, H. J. Singer6, H. U. Auster7, J. P. McFadden5, D. Larson5, and I. Mann8 K. Keika et al.
  • 1Space Research Institute, Austrian Academy of Sciences, Schmiedlstrasse 6, 8042 Graz, Austria
  • 2Center for Solar-Terrestrial Research, New Jersey Institute of Technology, 323 Martin-Luther-King Jr. Blvd., 101 Tiernan Hall, Newark, NJ 07102-1982, USA
  • 3Institute of Geophysics and Planetary Physics, University of California, Los Angeles, CA 90095, USA
  • 4Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency, Yoshinodai 3-1-1, Sagamihara 229-8510, Japan
  • 5Space Science Laboratory, University of California, 7 Gauss Way #7450, Berkeley, CA 94720-7450, USA
  • 6Space Weather Prediction Center, National Oceanic and Atmospheric Administration, 325 Broadway, Boulder, CO 80305, USA
  • 7Institut für Geophysik und extraterrestrische Physik, Technische Universität Braunschweig, Mendelssohnstr. 3, 38106 Braunschweig, Germany
  • 8Department of Physics, University of Alberta, 11322 – 89 Avenue, T6G 2G7 Edmonton, Alberta, Canada

Abstract. We examine fast plasma flows and magnetic field fluctuations observed by THEMIS at 03:00–03:30 UT on 12 December 2007. All THEMIS probes are situated in the near-Earth plasma sheet (XSM>−10 RE) with 1–2 RE spacecraft separations in azimuthal and radial directions. We focus on the observations of plasma convective flows made simultaneously by more than one THEMIS probe. At about 03:10 UT and 03:14 UT, the THEMIS P2 probe observed earthward flows of >100 km/s. The THEMIS P1 probe, located duskward and earthward of P2, observed tailward flows under a positive Bz. The inner most probe THEMIS P4, located at almost the same MLT as THEMIS P1 and P2, did not see any clear flow. We examine the convective flow patterns for the THEMIS observations. We conclude that plasma vortices are formed near the region where the earthward flows slow down and turn in azimuthal directions.