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Continuous magnetic reconnection at Earth's magnetopause


The most important process that allows solar-wind plasma to cross the magnetopause and enter Earth's magnetosphere is the merging between solar-wind and terrestrial magnetic fields of opposite sense—magnetic reconnection1. It is at present not known whether reconnection can happen in a continuous fashion or whether it is always intermittent. Solar flares2 and magnetospheric substorms3—two phenomena believed to be initiated by reconnection—are highly burst-like occurrences, raising the possibility that the reconnection process is intrinsically intermittent, storing and releasing magnetic energy in an explosive and uncontrolled manner. Here we show that reconnection at Earth's high-latitude magnetopause is driven directly by the solar wind, and can be continuous and even quasi-steady over an extended period of time. The dayside proton auroral spot in the ionosphere—the remote signature of high-latitude magnetopause reconnection4—is present continuously for many hours. We infer that reconnection is not intrinsically intermittent; its steadiness depends on the way that the process is driven.

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Figure 1: Diagram showing the link between reconnection at the magnetopause and its footprint in the ionosphere.
Figure 2: Snapshots of the proton aurora oval and spot on 18 March 2002 showing the continuous presence of the proton aurora spot.
Figure 3: Continuous presence of dayside proton aurora spot (and implied reconnection) for 4 h on 18 March 2002.
Figure 4: Continuous presence of dayside proton aurora spot (and implied reconnection) for 9 h on 17/18 September 2000.

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  1. Cowley, S. W. H. in Magnetic Reconnection in Space and Laboratory Plasmas (ed. Hones, E. W.) 375–378 (Geophysics Monograph 30, American Geophysical Union, Washington DC, 1984)

    Book  Google Scholar 

  2. Hudson, H. & Ryan, J. High-energy particles in solar flares. Annu. Rev. Astron. Astrophys. 33, 239–282 (1995)

    Article  ADS  Google Scholar 

  3. Angelopoulos, V. et al. Statistical characteristics of bursty bulk flow events. J. Geophys. Res. 103, 21257–21280 (1994)

    Article  ADS  Google Scholar 

  4. Phan, T. et al. Simultaneous Cluster and IMAGE observations of cusp reconnection and auroral proton spot for northward IMF. Geophys. Res. Lett. 30, doi:10.1029/2003GL016885 (2003)

  5. Scholer, M. Magnetic flux transfer at the magnetopause based on single X line bursty reconnection. Geophys. Res. Lett. 15, 291–294 (1988)

    Article  ADS  Google Scholar 

  6. Report of the NASA Science and Technology Definition Team for the Magnetospheric Multiscale (MMS) Mission (NASA/TM-2000–209883, Goddard Space Flight Center, Greenbelt, MD, 1999).

  7. Phan, T. D. et al. Extended magnetic reconnection at the Earth's magnetopause from detection of bi-directional jets. Nature 404, 848–850 (2000)

    Article  ADS  CAS  Google Scholar 

  8. Farrugia, C. J., Sandholt, P. E., Denig, W. F. & Torbert, R. B. Observation of a correspondence between poleward moving auroral forms and stepped cusp ion precipitation. J. Geophys. Res. 103, 9309–9315 (1998)

    Article  ADS  Google Scholar 

  9. Lockwood, M. et al. Cusp ion steps, field-aligned currents and poleward moving auroral forms. J. Geophys. Res. 106, 29555–29569 (2001)

    Article  ADS  Google Scholar 

  10. Lockwood, M., Davis, C. J., Onsager, T. G. & Scudder, J. D. Modelling signatures of pulsed magnetopause reconnection in cusp ion dispersion signatures seen at middle altitudes. Geophys. Res. Lett. 25, 591–594 (1998)

    Article  ADS  CAS  Google Scholar 

  11. Sandholt, P. E. et al. Dynamic cusp aurora and associated pulsed reverse convection during northward interplanetary magnetic field. J. Geophys. Res. 105, 12869–12894 (2000)

    Article  ADS  Google Scholar 

  12. Milan, S. E., Lester, M., Greenwald, R. A. & Sofko, G. The ionospheric signature of transient dayside reconnection and the associated pulsed convection return flow. Ann. Geophys. 17, 1166–1171 (1999)

    Article  ADS  Google Scholar 

  13. Frey, H. U. et al. Proton aurora in the cusp. J. Geophys. Res. A 107, doi:10.1029/2001JA900161 (2002)

  14. Fuselier, S. A. et al. Cusp aurora dependence on IMF Bz . J. Geophys. Res. A 107, doi:10.1029/2001JA900165 (2002)

    ADS  Google Scholar 

  15. Mende, S. B. et al. Far ultraviolet imaging from the IMAGE spacecraft: 3. Spectral imaging of Lyman alpha and OI 135.6 nm. Space Sci. Rev. 91, 287–318 (2000)

    Article  ADS  CAS  Google Scholar 

  16. Newell, P. T., Meng, C.-I., Sibeck, D. G. & Lepping, R. Some low-altitude cusp dependencies on the interplanetary magnetic field. J. Geophys. Res. 94, 8921–8927 (1989)

    Article  ADS  Google Scholar 

  17. Frey, H. U., Mende, S. B., Fuselier, S. A., Immel, T. J. & Ostgaard, N. Proton aurora in the cusp during southward IMF. J. Geophys. Res. A 108, doi:10.1029/2003JA009861 (2003)

  18. Mende, S. B., Rairden, R. L., Lanzerotti, L. J. & Maclennan, C. G. Magnetic impulses and associated optical signatures in the dayside aurora. Geophys. Res. Lett. 17, 131–134 (1990)

    Article  ADS  Google Scholar 

  19. Sandholt, P. E. IMF control of polar cusp and cleft auroras. Adv. Space Res. 8, 21–34 (1988)

    Article  ADS  Google Scholar 

  20. Newell, P. T. Do the dayside cusps blink? Rev. Geophys. Suppl. 33, 665–668 (1995)

    Article  ADS  Google Scholar 

  21. Lockwood, M. et al. IMF control of cusp proton emission intensity and dayside convection: Implications for component and anti-parallel reconnection. Ann. Geophys. 21, 955–982 (2003)

    Article  ADS  CAS  Google Scholar 

  22. Cowley, S. W. H. & Owen, C. J. A simple illustrative model of open flux tube motion over the dayside magnetopause. Planet. Space Sci. 37, 1461–1475 (1989)

    Article  ADS  Google Scholar 

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We are indebted to the IMAGE team and J. L. Burch for the design and successful operation of the IMAGE mission.

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Correspondence to H. U. Frey.

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Frey, H., Phan, T., Fuselier, S. et al. Continuous magnetic reconnection at Earth's magnetopause. Nature 426, 533–537 (2003).

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