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Ann. Geophys., 23, 2867-2875, 2005
www.ann-geophys.net/23/2867/2005/
© European Geosciences Union 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
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.
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