Skip to main content


We’d like to understand how you use our websites in order to improve them. Register your interest.

Evidence for an extended reconnection line at the dayside magnetopause


We report in-situ detection by two spacecraft of oppositely directed jets of plasma emanating from a magnetic reconnection site at the Earth’s dayside magnetopause, confirming a key element inherent in all reconnection scenarios. The dual-spacecraft (Equator-S and Geotail) observations at the flank magnetopause, together with SuperDARNHalley radar observations of the subsolar cusp region, reveal the presence of a rather stable and extended reconnection line which lies along the equatorial magnetopause. These observations were made under persistent southward interplanetary magnetic field (IMF) conditions, implying that under these conditions the reconnection sites are determined by the large-scale interactions between the solar wind magnetic field and the dayside magnetosphere, rather than by local conditions at the magnetopause. Control by local conditionswould result in patchy reconnection, distributed in a less well-organized fashion over the magnetopause surface.


  1. Andre, R., M. Pinnock, and A. S. Rodger, On the SuperDARN autocorrelation function observed in the cusp, Geophys. Res. Lett., 26, 3353–3356, 1999.

  2. Aubry, M. P., C. T. Russell, and M. G. Kivelson, Inward motion of the magnetopause before a substorm, J. Geophys. Res., 75, 7018–7031, 1970.

  3. Axford, W. I. and C. O. Hines, A unifying theory of high-latitude geophysical phenomena and geomagnetic storms, Canadian Journal of Physics, 39, 1433–1464, 1961.

  4. Baker, K. B., J. R. Dudeney, R. A. Greenwald, M. Pinnock, P. T. Newell, A. S. Rodger, N. Mattin, and C.-I. Meng, HF radar signatures of the cusp and low-latitude boundary layer, J. Geophys. Res., 100, 7671–7695, 1995.

  5. Burke, W. J., D. R. Weimer, and N. C. Maynard, Geoeffective interplanetary scale sizes derived from regression analysis of polar cap potentials, J. Geophys. Res., 104, 9989–9994, 1999.

  6. Crooker, N. U., Dayside merging and cusp geometry, J. Geophys. Res., 83, 951–959, 1979.

  7. Dungey, J. W., Interplanetary magnetic field and the auroral zones, Phys. Rev. Lett., 6, 47–48, 1961.

  8. Fairfield, D. H., Average and unusual locations of the Earth’s magnetopause and bow shock, J. Geophys. Res., 76, 6700, 1971.

  9. Fornacon, K.-H. et al., The magnetic field experiment onboard Equator-S and its scientific possibilities, Ann. Geophysicae., 17, 1521–1527, 1999.

  10. Frank, L. A. et al., The comprehensive plasma instrumentation (CPI) for the Geotail spacecraft, J. Geomag. Geoelectr., 46, 23–37, 1994.

  11. Giovanelli, R. G., A theory of chromospheric flares, Nature, 158, 81–82, 1946.

  12. Gonzales, W. D. and F. S. Mozer, A quantitative model for the potential resulting from reconnection with an arbitrary interplanetary magnetic field, J. Geophys. Res., 79, 4186–4194, 1974.

  13. Gosling, J. T. et al., Accelerated plasma flows at the near-tail magnetopause, J. Geophys. Res., 91, 3029–3041, 1986.

  14. Greenwald, R. A., K. B. Baker, J. R. Dudeney, M. Pinnock, T. B. Jones, E. C. Thomas, J.-P. Villain, J.-C. Cerisier, C. Senior, C. Hanuise, R. D. Hunsucker, G. Sofko, J. Koehler, E. Nielsen, R. Pellinen, A. D. M. Walker, N. Sato, and H. Yamagishi, DARN/SuperDARN: A global view of the dynamics of high-latitude convection, Space Science Rev., 71, 761–796, 1995.

  15. Hudson, P. D., Discontinuities in an anisotropic plasma and their identification in the solar wind, Planet. Space Sci., 18, 1611, 1970.

  16. Innes, D. E. et al., Bi-directional plasma jets produced by magnetic reconnection on the Sun, Nature, 386, 811–813, 1997.

  17. Kistler, L. M. et al, Testing Electric Field Models Using Ring Current Ion Energy Spectra from the Equator-S Ion Composition (ESIC) Experiment, Ann. Geophys., 12, 1611–1621, 1999.

  18. Kokubun, S. et al, The GEOTAIL magnetic field experiment, J. Geomag. Geoelectr., 46, 7, 1994.

  19. Levy, R. H., H. E. Petschek, and G. L. Siscoe, Aerodynamic aspects of the magnetospheric flow, AIAA J., 2, 2065, 1964.

  20. Masuda, S., et al, A loop-top hard X-ray source in a compact solar flare as evidence for magnetic reconnection, Nature, 371, 495–497, 1994.

  21. Mukai, S., et al., The Low Energy Particle (LEP) experiment onboard the GEOTAIL Satellite, J. Geomag. Geoelectr, 46, 669, 1994.

  22. Niedner, M. B., J. A. Ionson, and J. C. Brandt, Interplanetary Gas. XXVI. On the reconnection of magnetic fields in cometary ionospheres at interplanetary sector boundary crossings, Astrophys. J., 245, 1159–1169, 1981.

  23. Paschmann, G., et al, Plasma acceleration at the earth’s magnetopause: Evidence for reconnection, Nature, 282, 243–246, 1979.

  24. Paschmann, G., et al., The magnetopause for large magnetic shear: AMPTE/IRM observations, J. Geophys. Res., 91, 11099, 1986.

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

  26. Siscoe, G. L. and T. S. Huang, Polar cap inflation and deflation, J. Geophys. Res., 90, 543, 1985.

  27. Sonnerup, B. U. Ö., The magnetopause reconnection rate, J. Geophys. Res., 79, 1546–1549, 1974.

  28. Sonnerup, B. U. Ö., et al, Evidence for reconnection at the earth’s magnetopause, J. Geophys. Res., 86, 10049–10067, 1981.

  29. Yokoyama, T. and K. Shibata, Magnetic field reconnection as the origin of X-ray jets and H-Alpha surges on the sun, Nature, 375, 42, 1995.

Download references

Author information



Corresponding author

Correspondence to T. D. Phan.

Rights and permissions

Reprints and Permissions

About this article

Verify currency and authenticity via CrossMark

Cite this article

Phan, T.D., Freeman, M.P., Kistler, L.M. et al. Evidence for an extended reconnection line at the dayside magnetopause. Earth Planet Sp 53, 619–625 (2001).

Download citation


  • Solar Wind
  • Interplanetary Magnetic Field
  • Universal Time
  • Reconnection Site
  • Dayside Magnetopause