Abstract
A saddle-like structure is clearly discerned in SOHO EIT images in the Fe wavebands in the active region NOAA 8113, from 6 to 10 December 1997, when the active region reached the solar limb. It appears after the emergence of a small patch of parasitic polarity near the footpoints of the loops forming the outer boundary of an arcade. There is a 3D null point in the center of the saddle. The height of the null is in good agreement with the relationship between the parasitic flux and the background magnetic field. In spite of the fact that a saddle-like or hyperbolic magnetic configuration is usually assumed as the necessary condition for magnetic field-line reconnection and magnetic energy release, no additional heating is observed inside the saddle structure. Moreover, interior parts of the saddle seem to be darker than the neighbouring loops of the arcade.
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References
Biskamp, D.: 1982, Phys. Letters 87A, 357.
Biskamp, D.: 1984, Phys. Letters 105A, 124.
Démoulin, P., Hénoux, J. C., and Mandrini, C. H.: 1994, Astron. Astrophys. 285, 1023.
Démoulin, P., van Driel-Gesztelyi, L., Schmieder, B., Hénoux, J. C., Csepura, G., and Hagyard, M. J.: 1993, Astron. Astrophys. 271, 292.
Dungey, J. W.: 1953, Phil. Mag. 44, 725.
Filippov, B. P.: 1995, Astron. Astrophys. 303, 242.
Filippov, B. P. and Shilova, N. S.: 1997, Astron. Reports 41, 126.
Fukao, S., Masayuki, U., and Takao, T.: 1975, Rep. Ionospheric Space Res. Japan 29, 133.
Galsgaard, K. and Nordlund, A.: 1997, J. Geophys. Res. 102, 231.
Galsgaard, K., Reddy, R. V., and Rickard, G. J.: 1997, Solar Phys. 176, 299.
Giovanelli, R. G.: 1947, Monthly Notices Royal Astron. Soc. 107, 338.
Giovanelli, R. G.: 1948, Monthly Notices Royal Astron. Soc. 108, 163.
Greene, J. M.: 1989, J. Geophys. Res. 93, 8583.
Jardine, M. and Priest, E. R.: 1988,J. Plasma Phys. 40, 143.
Lau, Y. T. and Finn, J. M.: 1990, Astrophys. J. 350, 672.
Lee, L. C. and Fu, Z. F.: 1986, Geophys. Res. Letters 12, 2.
Moses, D., Clette, F., Delaboudiniere, J.-P., Artzner, G. E. et al.: 1997, Solar Phys. 175, 571.
Parker, E. N.: 1957, J. Geophys. Res. 62, 509.
Parker, E. N.: 1973, J. Plasma Phys. 9, 49.
Parnell, C. E., Smith, J. M., Neukirch, T., and Priest E. R.: 1996, Phys. Plasma 3, 759.
Petschek, H. E.: 1964, AAS-NASA Symposium on Solar Flares, NASA SP-50, p. 425.
Priest, E. R. and Forbes, T. G.: 1986, J. Geophys. Res. 91, 5579.
Priest, E. R. and Titov, V. S.: 1996, Phil. Trans. Roy. Soc. London A354, 2951.
Scholer, M.: 1989, J. Geophys. Res. 94, 8805.
Severny, A. B.: 1958, Astron. Zh. 35, 335.
Simnett, G. M., Tappin, S. J., Plunkett, S. P., Bedford, K. et al.: 1997, Solar Phys. 175, 685.
Somov, B. V.: 1986, Astron. Astrophys. 163, 210.
Sonnerup, B. U. O.: 1970, J. Plasma Phys. 4, 161.
Sweet, P. A.: 1958, in B. Lehnert (ed.), Electromagnetic Phenomena in Cosmic Physics, Cambridge University Press, Cambridge, p. 124.
Sweet, P. A.: 1969, Ann. Rev. Astron. Astrophys. 7, 149.
Syrovatsky, S. I.: 1966, Astron. Zh. 43, 340.
Tsuneta, S.: 1996, Astrophys. J. 456, 840.
Tsuneta, S., Hara, H., Shimizu, T., Acton, L., Strong, K., Hudson, H., and Ogawara, Y.: 1992, Publ. Astron. Soc. Japan 44, L63.
Wang, H.-N. and Wang, J.-X.: 1996, Astron. Astrophys. 313, 285.
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Filippov, B. Observation of a 3d Magnetic Null Point in the Solar Corona. Solar Physics 185, 297–309 (1999). https://doi.org/10.1023/A:1005124915577
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DOI: https://doi.org/10.1023/A:1005124915577