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A magnetic reconnection X-line extending more than 390 Earth radii in the solar wind

Nature volume 439, pages 175–178 (2006)Cite this article

Abstract

Magnetic reconnection in a current sheet converts magnetic energy into particle energy, a process that is important in many laboratory1, space2,3 and astrophysical contexts4,5,6. It is not known at present whether reconnection is fundamentally a process that can occur over an extended region in space or whether it is patchy and unpredictable in nature7. Frequent reports of small-scale flux ropes and flow channels associated with reconnection8,9,10,11,12,13 in the Earth's magnetosphere raise the possibility that reconnection is intrinsically patchy, with each reconnection X-line (the line along which oppositely directed magnetic field lines reconnect) extending at most a few Earth radii (RE), even though the associated current sheets span many tens or hundreds of RE. Here we report three-spacecraft observations of accelerated flow associated with reconnection in a current sheet embedded in the solar wind flow, where the reconnection X-line extended at least 390RE (or 2.5 × 106 km). Observations of this and 27 similar events imply that reconnection is fundamentally a large-scale process. Patchy reconnection observed in the Earth's magnetosphere is therefore likely to be a geophysical effect associated with fluctuating boundary conditions, rather than a fundamental property of reconnection. Our observations also reveal, surprisingly, that reconnection can operate in a quasi-steady-state manner even when undriven by the external flow.

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Figure 1: Diagram of the encounters of three spacecraft with an extended (390 R E ) magnetic reconnection X-line in the solar wind.
Figure 2: Detections of the magnetic reconnection exhaust by the ACE, Cluster-3 and Wind spacecraft on 2 February 2002.
Figure 3: Quantitative comparison between the flow acceleration observed by the Wind spacecraft and the prediction from reconnection.

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Acknowledgements

Wind, ACE and Cluster research in the US is supported by NASA. Cluster research in France and the UK is supported by CNES and PPARC.

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Authors and Affiliations

  1. Space Sciences Laboratory, University of California, California, 94720, Berkeley, USA

    T. D. Phan, M. S. Davis, M. Øieroset & R. P. Lin

  2. Laboratory for Atmospheric and Space Physics, University of Colorado, Colorado, 80303, Boulder, USA

    J. T. Gosling

  3. Los Alamos National Laboratory, MS D466, New Mexico, 87545, Los Alamos, USA

    R. M. Skoug

  4. Laboratory for Solar and Space Physics, NASA/Goddard Space Flight Center, Maryland, 20771, Greenbelt, USA

    R. P. Lepping

  5. Space Science and Engineering Division, Southwest Research Institute, PO Drawer 28510, Texas, 78228, San Antonio, USA

    D. J. McComas

  6. Department of Physics and Space Science Center, University of New Hampshire, Room 207 Morse Hall, 30 College Road, New Hampshire, 03824, Durham, USA

    C. W. Smith

  7. Centre d'Etude Spatiale des Rayonnements, BP 4346, 31029, Toulouse, France

    H. Reme

  8. Space and Atmospheric Physics Group, Imperial College, SW7 2BZ, London, UK

    A. Balogh

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  1. T. D. Phan
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Correspondence to T. D. Phan.

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Phan, T., Gosling, J., Davis, M. et al. A magnetic reconnection X-line extending more than 390 Earth radii in the solar wind. Nature 439, 175–178 (2006). https://doi.org/10.1038/nature04393

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