Skip to main content


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

The nature of Petschek-type reconnection


It is not always appreciated that Petschek’s reconnection mechanism is a particular solution of the MHD equations which applies only when special conditions are met. Specifically, it requires that the flow into the reconnection region be set up spontaneously without external forcing. This condition is satisfied when reconnection in a simple current sheet is initiated by enhancing the resistivity in a localized region. Such a process disrupts the current sheet and launches slow-mode waves which steepen into nearly switch-off shocks of the type predicted by Petschek. As these shocks propagate outwards, the current sheet reforms at the original point of the disturbance, and a quasi-steady Petschek-like configuration is set up. Syrovatskii-like configurations which force reconnection by driving a flow toward an initially current-free, orthogonal x-point are less likely to satisfy the conditions required for Petschek-type reconnection.


  1. Biernat, H. K. and M. F. Heyn, Unsteady Petschek reconnection, J. Geophys. Res., 92, 3392–3396, 1987.

  2. Biskamp, D., Magnetic reconnection via current sheets, Phys. Fluids, 29, 1520–1531, 1986.

  3. Erkaev, N. V., V. S. Semenov, and F. Jamitzky, Reconnection rate for the inhomogeneous resistivity Petschek model, Phys. Rev. Lett., 84, 1455–1458, 2000.

  4. Green, R. M., Modes of annihilation and reconnection of magnetic fields, in Solar and Stellar Magnetic Fields, edited by R. Lüst, pp. 398–404, North-Holland Publishing Co., Amsterdam, 1965.

  5. Heyn, M. F. and V. S. Semenov, Rapid reconnection in compressible plasma, Phys. Plasmas, 3, 2725–2741, 1996.

  6. Jin, S.-P. and W.-H. Ip, Two-dimensional compressible magnetohydrodynamic simulation of the driven reconnection process, Phys. Fluids B, 3, 1927–1936, 1991.

  7. Lee, L. C. and Z. F. Fu, Multiple x-line reconnection, 1. A criterion for the transition from a single x-line to a multiple x-line reconnection, J. Geophys. Res., 91, 6807–6815, 1986.

  8. Litvinenko, Y. E. and I. J. D. Craig, Magnetic energy release in flux pile-up merging, Solar Phys., 189, 315–329, 1999.

  9. Parker, E. N., Sweet’s mechanism for merging magnetic fields in conducting fluids, J. Geophys. Res., 62, 509–520, 1957.

  10. Parker, E. N., Comments on the reconnexion rate of magnetic fields, J. Plasma Phys., 9, 49–63, 1973.

  11. Petschek, H. E., Magnetic field annihilation, in The Physics of Solar Flares, edited by W. N. Hess, pp. 425–439, NASA, SP-50, 1964.

  12. Priest, E. R. and T. G. Forbes, New models for fast steady-state magnetic reconnection, J. Geophys. Res., 91, 5579–5588, 1986.

  13. Priest, E. R. and T. G. Forbes, Does fast magnetic reconnection exist?, J. Geophys. Res., 97, 16757–16772, 1992.

  14. Priest, E. R. and T. G. Forbes, Magnetic Reconnection—MHD Theory and Applications, 600 pp., Cambridge Univ. Press, Cambridge, 2000.

  15. Rijnbeek, R. P. and V. S. Semenov, Features of a Petschek-type reconnection model, Trends in Geophys. Res., 2, 247–268, 1993.

  16. Sato, T., Strong plasma acceleration by slow shocks resulting from magnetic reconnection, J. Plasma Phys., 30, 109–124, 1983.

  17. Scholer, M., Undriven magnetic reconnection in an isolated current sheet, J. Geophys. Res., 94, 8805–8812, 1989.

  18. Schumacher, J. and B. Kliem, Dynamic current sheets with localized anomalous resistivity, Phys. Plasmas, 3, 4703–4711, 1996.

  19. Semenov, V. S., M. F. Heyn, and I. V. Kubyshkin, Reconnection of magnetic field lines in a nonstationary case, Sov. Astron., 27, 660–665, 1983.

  20. Semenov, V. S., E. P. Vasilyev, and A. I. Purovkin, A scheme for the non-steady reconnection of magnetic lines of force, Geomagnet. Aeronomy (Engl. Transl), 24, 370–373, 1984.

  21. Somov, B. V., Physical Processes in Solar Flares, 249 pp., Kluwer, Dordrecht, 1992.

  22. Sonnerup, B. U., Ö., Magnetic-field reconnection in a highly conducting incompressible fluid, J. Plasma Phys., 4, 161–174, 1970.

  23. Soward, A. M. and E. R. Priest, Fast magnetic field-line reconnection in a compressible fluid, 1, Coplanar field lines, J. Plasma Phys., 28, 335–367, 1982.

  24. Strachan, N. and E. R. Priest, A general family of nonuniform reconnection models with separatrix jets, Geophys. Astrophys. Fluid Dynamics, 74, 245, 1994.

  25. Sweet, P. A., The neutral point theory of solar flares, in Electromagnetic Phenomenon in Cosmical Physics, edited by B. Lehnert, pp. 123–139, Cambridge Univ. Press, New York, 1958.

  26. Syrovatskii, S. I., Formation of current sheets in a plasma with a frozen-in strong magnetic field, Sov. Phys. JETP (Engl. Transl.), 33, 933–940, 1971.

  27. Ugai, M., Self-consistent development of fast magnetic reconnection with anomalous plasma resistivity, Plasma Phys. Contr. Fusion, 26, 1549, 1984.

  28. Ugai, M., MHD simulations of fast reconnection spontaneously developing in a current sheet, Computer Phys. Communications, 49, 185–192, 1988.

  29. Ugai, M., Computer studies on plasmoid dynamics associated with the spontaneous fast reconnection mechanism, Phys. Plasmas, 2, 3320–3328, 1995.

  30. Ugai, M. and T. Tsuda, Magnetic field-line reconnexion by localized enhancement of resistivity. I - Evolution in a compressible MHD fluid, J. Plasma Phys., 17, 337–356, 1977.

  31. Vasyliunas, V. M., Theoretical models of magnetic field line merging, 1, Rev. Geophys., 13, 303–336, 1975.

  32. Yan, M., L. C. Lee, and E. R. Priest, Fast magnetic reconnection with small shock angles, J. Geophys. Res., 97, 8277–8293, 1992.

Download references

Author information



Corresponding author

Correspondence to T. G. Forbes.

Rights and permissions

Reprints and Permissions

About this article

Verify currency and authenticity via CrossMark

Cite this article

Forbes, T.G. The nature of Petschek-type reconnection. Earth Planet Sp 53, 423–429 (2001).

Download citation


  • Mach Number
  • Current Sheet
  • Magnetic Reconnection
  • Diffusion Region
  • Magnetic Reynolds Number