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AGU: Journal of Geophysical Research, Space Physics

 

Keywords

  • traveling compression region
  • TCR
  • NENL

Index Terms

  • Magnetospheric Physics: Magnetic storms and substorms
  • Magnetospheric Physics: Magnetotail
  • Ionosphere: Auroral ionosphere
Abstract
Cited By (11)
 

Abstract

Cluster observations of traveling compression regions in the near-tail

J. A. Slavin

Laboratory for Extraterrestrial Physics, NASA Goddard Space Flight Center, Greenbelt, Maryland, USA

E. I. Tanskanen

Laboratory for Extraterrestrial Physics, NASA Goddard Space Flight Center, Greenbelt, Maryland, USA

M. Hesse

Laboratory for Extraterrestrial Physics, NASA Goddard Space Flight Center, Greenbelt, Maryland, USA

C. J. Owen

Mullard Space Science Laboratory, University College London, Surrey, UK

M. W. Dunlop

Rutherford Appleton Laboratory, Oxfordshire, UK

S. Imber

Space and Atmospheric Physics, Imperial College, London, UK

E. A. Lucek

Space and Atmospheric Physics, Imperial College, London, UK

A. Balogh

Space and Atmospheric Physics, Imperial College, London, UK

K.-H. Glassmeier

Institut für Geophysik und extraterrestrische Physik, Technische Universität Braunschweig, Braunschweig, Germany

Examination of Cluster measurements has revealed the presence of traveling compression regions (TCRs) in the lobes of the Earth's magnetotail at X ∼ −11–19 R E . These TCRs strongly resemble those observed in the more distant tail, but their mean duration is only ∼35 s as compared with ∼160 s for the TCRs in the distant tail. Furthermore, the B z variations associated with the Cluster TCRs were found to be south-then-north (SN) in 80% of the cases as opposed to the north-then-south (NS) polarity that is dominant beyond X ∼ −30 R E . Analysis of the time of arrival of the TCRs at the different Cluster spacecraft showed that all of the SN TCRs propagate earthward while all of the NS TCRs, as expected, move tailward. The mean speeds of the SN and NS TCRs were essentially the same, 849 km/s and 821 km/s, respectively, and their average width was 4.3 R E . Some examples of near-periodic, multiple TCR events with separations between individual TCRs comparable to their width were also observed, suggestive of multiple X-line reconnection or periodic impulsive reconnection. However, the most probable separation observed during multi-TCR events was larger, ∼100–150 s. The TCR minimum variance eigenvectors have a strong tendency to lie parallel to the GSM XY plane, but they exhibit a wide range of orientations within that plane. Examined as a function of the Y GSM, there are broad maxima in occurrence frequency, width, and speed of TCRs on the duskside of the tail. Superposed epoch analysis of the Kyoto World Data Center Quick Look AL Index relative to the time of TCR occurrence shows that the compression regions tend to be observed during the expansion phase of substorms. Finally, the origins of the traveling compression regions in the near-tail are discussed in terms of the effects of magnetic flux rope motion and impulsive reconnection.

Received 14 February 2004; accepted 17 March 2005; published 11 June 2005.

Citation: Slavin, J. A., E. I. Tanskanen, M. Hesse, C. J. Owen, M. W. Dunlop, S. Imber, E. A. Lucek, A. Balogh, and K.-H. Glassmeier (2005), Cluster observations of traveling compression regions in the near-tail, J. Geophys. Res., 110, A06207, doi:10.1029/2004JA010878.

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