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Volume 53 Supplement 6

Special Issue: Magnetic Reconnection in Space and Laboratory Plasmas

Solar flare mechanism based on magnetic arcade reconnection and island merging


We propose a model describing physical processes of solar flares based on resistive reconnection of magnetic field subject to continuous increase of magnetic shear in the arcade. The individual flaring process consists of magnetic reconnection of arcade field lines, generation of magnetic islands in the magnetic arcade, and coalescence of magnetic islands. When a magnetic arcade is sheared (either by footpoint motion or by flux emergence), a current sheet is formed and magnetic reconnection can take place to form a magnetic island. A continuing increase of magnetic shear can trigger a new reconnection process and create a new island in the underlying arcade below the magnetic island. The newborn island rises faster than the preceding island and merges with it to form one island. Before completing the island merging process, the newborn island exhibits two phases of rising motion: a first phase with a slower rising speed and a second phase with a faster rising speed. The flare plasma heating occurs mainly due to magnetic reconnection in the current sheet under the newborn island. The newborn island represents the X-ray plasma ejecta which shows two phases of rising motion observed by Yohkoh (Ohyama and Shibata, 1997). The first phase with slower newborn island rising speed corresponds to the early phase of reconnection of line-tied field in the underlying current sheet and is considered as the preflare phase. In the second phase, the island coalescence takes place, and the underlying current sheet is elongated so that the line-tied arcade field reconnection rate is enhanced. This phase is interpreted as the impulsive phase or the flash phase of flares. The obtained reconnection electric field is large enough to accelerate electrons to an energy level higher than 10 keV, which is necessary for observed hard X-ray emissions. After merging of the islands is completed, magnetic reconnection continues in the current sheet under the integrated island for a longer period, which is considered as the main phase of flares. The sequence of all these processes is repeated with some time interval while a shear-increasing motion continues. We propose that these repetitive flaring processes constitute a set of homologous flares.


  • Amari, T., J. F. Luciani, J. J. Aly, and M. Tagger, Plasmoid formation in a single sheared arcade and application to coronal mass ejections, Astron. Astrophys., 306, 913–923, 1996.

    Google Scholar 

  • Anzer, U., Models of structure and dynamics of prominences, in Physics of Solar Prominences, IAU Colloquium 44, edited by E. Jensen, P. Maltby, and F. Q. Orrall, p. 322, Blindern-Oslo, Institute of Theoretical Astrophysics, 1979.

  • Cheng, C. Z. and G. S. Choe, Current sheets and prominence formation in the solar atmosphere, Astrophys. J., 505, 376–389, 1998.

    Article  Google Scholar 

  • Choe, G. S. and C. Z. Cheng, A model of solar flares and their homologous behavior, Astrophys. J., 541, 449–467, 2000.

    Article  Google Scholar 

  • Choe, G. S. and L. C. Lee, Formation of solar prominences by photospheric shearing motions, Solar. Phys., 138, 291–329, 1992.

    Article  Google Scholar 

  • Choe, G. S. and L. C. Lee, Evolution of solar magnetic arcades. II. Effect of resistivity and solar eruptive processes, Astrophys. J., 472, 372–388, 1996.

    Article  Google Scholar 

  • Forbes, T. G., Numerical simulation of a catastrophe model for coronal mass ejections, J. Geophys. Res., 95, 11919–11931, 1990.

    Article  Google Scholar 

  • Gold, T. and F. Hoyle, On the origin of solar flares, Mon. Not. R. Aston. Soc., 120, 89–105, 1960.

    Article  Google Scholar 

  • Inhester, B., J. Birn, and M. Hesse, The evolution of line-tied coronal arcades including a converging footpoint motion, Solar. Phys., 138, 257–281, 1992.

    Article  Google Scholar 

  • Kane, S. R., Impulsive flash phase of solar flares: Hard X-ray, microwave, EUV and optical observations, in Coronal Disturbances, IAU Symposium No. 57, edited by G. A. Newkirk, p. 105, Dordrecht, D. Reidel, 1974.

    Chapter  Google Scholar 

  • Kopp, R. A. and G. W. Pneuman, Magnetic reconnection in the corona and the loop prominence phenomenon, Solar. Phys., 50, 85–98, 1976.

    Article  Google Scholar 

  • Kuperus, M. and M. A. Raadu, The support of prominences formed in neutral sheets, Astron. Astrophys., 31, 189–193, 1974.

    Google Scholar 

  • Linker, J. A. and Z. Mikićion of a helmet streamer by photospheric shear, Astrophys. J., 438, L45–48, 1995.

    Article  Google Scholar 

  • Magara, T., K. Shibata, and T. Yokoyama, Evolution of eruptive flares. I. Plasmoid dynamics in eruptive flares, Astrophys. J., 487, 437–446, 1997.

    Article  Google Scholar 

  • Masuda, S., T. Kosugi, H. Hara, S. Tsuneta, and Y. Ogawara, A loop-top hard X-ray source in a compact solar flare as evidence for magnetic reconnection, Nature, 371, 495–497, 1994.

    Article  Google Scholar 

  • Mikić J. A. Linker, Disruption of coronal magnetic arcades, Astrophys. J., 430, 898–912, 1994.

    Article  Google Scholar 

  • Mikic, Z., D. C. Barnes, and D. Schnack, Dynamical evolution of a solar coronal magnetic field arcade, Astrophys. J., 328, 830–847, 1988.

    Article  Google Scholar 

  • Ohyama, M. and K. Shibata, Preflare heating and mass motion in a solar flare associated with hot plasma ejection: 1993, November 11 C9.7 flare, Pub. Astron. Soc. Japan, 49, 249–261, 1997.

    Article  Google Scholar 

  • Priest, E. R., Solar Magnetohydrodynamics, D. Reidel, Dordrecht, 1982.

    Book  Google Scholar 

  • Priest, E. R. and T. G. Forbes, Magnetic field evolution during prominence eruptions and two-ribbon flares, Solar. Phys., 126, 319–350, 1990.

    Article  Google Scholar 

  • Shibata, K., A unified model of solar flares, in Observational Plasma Astrophysics: Five Years of Yohkoh and Beyond, edited by T. Watanabe, T. Kosugi, and A. C. Sterling, p. 187, Boston, Kluwer Academic Publishers, 1998.

    Chapter  Google Scholar 

  • Shibata, K., S. Masuda, M. Shimojo, H. Hara, T. Yokoyama, S. Tsuneta, T. Kosugi, and Y. Ogawara, Hot-plasma ejections associated with compact-loop solar flares, Astrophys. J., 451, L83–85, 1995.

    Google Scholar 

  • Sturrock, P. A., A model of solar flares, in Structure and Development of Solar Active Regions, IAU Symposium No. 35, edited by K. O. Kiepenheuer, p. 471, Dordrecht, D. Reidel, 1968.

    Chapter  Google Scholar 

  • Tsuneta, S., Structure and dynamics of magnetic reconnection in a solar flare, Astrophys. J., 456, 840–849, 1996.

    Article  Google Scholar 

  • Van Tend, W. and M. Kuperus, The development of coronal electric current systems in active regions and their relation to filaments and flares, Solar. Phys., 59, 115–127, 1978.

    Article  Google Scholar 

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Cheng, C.Z., Choe, G.S. Solar flare mechanism based on magnetic arcade reconnection and island merging. Earth Planet Sp 53, 597–604 (2001).

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  • Current Sheet
  • Solar Flare
  • Magnetic Reconnection
  • Impulsive Phase
  • Reconnection Process