Articles | Volume 23, issue 3
Ann. Geophys., 23, 997–1011, 2005
Ann. Geophys., 23, 997–1011, 2005

  30 Mar 2005

30 Mar 2005

Correlation between ground-based observations of substorm signatures and magnetotail dynamics

E. Borälv1, H. J. Opgenoorth1,9, K. Kauristie2, M. Lester3, J.-M. Bosqued4, J. P. Dewhurst5, C. J. Owen5, M. Dunlop6,8, J. A. Slavin7, A. Fazakerley5, and C. Perry8 E. Borälv et al.
  • 1Swedish Institute of Space Physics, Uppsala, Sweden
  • 2Finnish Meteorological Institute, Space Research, Helsinki, Finland
  • 3University of Leicester, Department of Physics and Astronomy, Leicester, UK
  • 4Centre d’Etude Spatiale des Rayonnements, Toulouse, France
  • 5Mullard Space Science Laboratory, University College London, Surrey, UK
  • 6Space and Atmospheric Physics, Blackett Laboratory, Imperial College, London, UK
  • 7NASA Goddard Space Flight Center, Laboratory for Extraterrestrial Physics, Maryland, USA
  • 8Space Science Department, Rutherford Appleton Laboratory, Oxfordshire, UK
  • 9European Space Agency, ESTEC, Noordwijk, Netherlands

Abstract. We present a substorm event study using the four Cluster spacecraft in combination with ground-based instruments, in order to perform simultaneous observations in the ionosphere and magnetotail. We show good correlation between substorm signatures on the ground and in the magnetotail, even though data from the northern-ground and southern-tail hemispheres are compared. During this event ground-based magnetometers show a substorm onset over Scandinavia in the pre-midnight sector. Within 1.5h the onset and three intensifications are apparent in the magnetograms. For all the substorm signatures seen on the ground, corresponding plasma sheet boundary motion is visible at Cluster, located at a downtail distance of 18.5 RE. As a result of the substorm onset and intensifications, Cluster moves in and out between the southern plasma sheet and lobe. Due to the lack of an apparent solar wind driver and the good correlation between substorm signatures on the ground, we conclude the substorm itself is the driver for these plasma sheet dynamics. We show that in the scales of Cluster inter-spacecraft distances (~0.5 RE) the inferred plasma sheet motion is often directed in both Ygsm- and Zgsm-directions, and discuss this finding in the context of previous studies of tail flapping and plasma sheet thickness variations.