Articles | Volume 23, issue 8
Ann. Geophys., 23, 2867–2875, 2005

Special issue: Double Star - First Results

Ann. Geophys., 23, 2867–2875, 2005

  08 Nov 2005

08 Nov 2005

Coordinated Cluster/Double Star observations of dayside reconnection signatures

M. W. Dunlop1,2, M. G. G. T. Taylor3, J. A. Davies1, C. J. Owen3, F. Pitout4, A. N. Fazakerley3, Z. Pu5, H. Laakso4, Y. V. Bogdanova3, Q.-G. Zong6, C. Shen7, K. Nykyri2, B. Lavraud8, S. E. Milan9, T. D. Phan10, H. Rème11, C. P. Escoubet4, C. M. Carr2, P. Cargill2, M. Lockwood1, and B. Sonnerup12 M. W. Dunlop et al.
  • 1Space Science and Technology Department, Rutherford Appleton Laboratory, Chilton, Oxfordshire, OX11 0QX, UK
  • 2The Blackett Laboratory, Imperial College London, London, SW7 2AZ, UK
  • 3Mullard Space Science Laboratory, University College London, Dorking, Surrey, RH5 6NT, UK
  • 4ESA/ESTEC, Keplerlaan 1, 2200 AG Noordwijk, The Netherlands
  • 5School of Earth and Space Sciences, Peking University, Beijing 100871, China
  • 6Centre for Space Physics, Boston University, Boston, Massachusetts, MA 02215, USA
  • 7Centre for Space Science and Applied Research, Chinese Academy of Sciences, Beijing 100080, China
  • 8Space Science and Applications, Los Alamos National Laboratory, Los Alamos, NM 87545, USA
  • 9Department of Physics and Astronomy, University of Leicester, Leicester, LE1 7RH, UK
  • 10Space Sciences Laboratory, University of California, Berkeley, California, CA 94720, USA
  • 11Centre d’Etude Spatiale des Rayonnements, Toulouse Cedex 4, France
  • 12Thayer School of Engineering, Dartmouth College, Hanover, New Hampshire, NH 03755, USA

Abstract. The recent launch of the equatorial spacecraft of the Double Star mission, TC-1, has provided an unprecedented opportunity to monitor the southern hemisphere dayside magnetopause boundary layer in conjunction with northern hemisphere observations by the quartet of Cluster spacecraft. We present first results of one such situation where, on 6 April 2004, both Cluster and the Double Star TC-1 spacecraft were on outbound transits through the dawnside magnetosphere. The observations are consistent with ongoing reconnection on the dayside magnetopause, resulting in a series of flux transfer events (FTEs) seen both at Cluster and TC-1, which appear to lie north and south of the reconnection line, respectively. In fact, the observed polarity and motion of each FTE signature advocates the existence of an active reconnection region consistently located between the positions of Cluster and TC-1, with Cluster observing northward moving FTEs with +/- polarity, whereas TC-1 sees -/+ polarity FTEs. This assertion is further supported by the application of a model designed to track flux tube motion for the prevailing interplanetary conditions. The results from this model show, in addition, that the low-latitude FTE dynamics are sensitive to changes in convected upstream conditions. In particular, changing the interplanetary magnetic field (IMF) clock angle in the model suggests that TC-1 should miss the resulting FTEs more often than Cluster and this is borne out by the observations.