Abstract
A model of a coronal region of enhanced Fexv and Fexvi emission is developed and its energy balance is examined using extreme ultraviolet observations from OSO-7 together with calculations of possible force-free coronal magnetic field configurations. The coronal emissions overlying the photospheric boundary between regions of opposite magnetic polarity are found to be associated with generally non-potential (current-carrying) magnetic fields in the forms of arches with footpoints in regions of opposite polarity. The orientation of these arches relative to the neutral line changes with degree of ionization of the emitting ion (which we infer from our limb observations to be a function of height) and may be evidence of differing electric currents along various field lines. The appearance of a coronal arch, seen side-on, can conveniently be represented by a parabola and a detailed analysis (Appendix) shows this to be a realistic approximation that should be generally useful in analyzing two-dimensional pictures of coronal structures. Applying this analysis to the most prominent coronal region observed in the radiations of Fexv and Fexvi, we find a maximum in the electron temperature, T e , of 2.6 × 106K at the top of arches whose heights are 20000–40000 km and whose footpoints are separated by ≈ 100000 km. A temperature gradient of ▽T e ≈5 × 10-5K cm-1 is found in this coronal structure. Radiative losses are typically fifteen times greater than conductive losses and the energy deposition required to maintain the coronal feature is nearly uniformly distributed along its length.
This is a preview of subscription content, log in via an institution to check access.
Similar content being viewed by others
References
Acton, L. W., Catura, R. C., Meyerott, A. J., Wolfson, L. J., and Culhane, J. L.: 1972, Solar Phys. 26, 183.
Alfvén, H.: 1947, Monthly Notices Roy. Astron. Soc. 107, 211.
Batstone, R. M., Evans, R., Parkinson, J. H., and Pounds, K. A.: 1970, Solar Phys. 13, 389.
Bely, O. and Blaha, M.: 1968, Solar Phys. 3, 563.
Billings, D. E.: 1966, A Guide to the Solar Corona, Academic Press, New York.
Boardman, W. J. and Billings, D. E.: 1969, Astrophys. J. 156, 731.
Chambe, G.: 1971, Astron. Astrophys. 12, 210.
Chapman, R. D. and Neupert, W. M.: 1974, J. Geophys. Res. 79, 4138.
Cox, D. P. and Tucker, W. H.: 1969, Astrophys. J. 157, 1157.
Davis, J. M.: 1975, private communication.
Dupree, A. K. and Goldberg, L.: 1967, Solar Phys. 1, 229.
Hirayama, T.: 1971, Solar Phys. 17, 50.
Ivanov-Kholodnyi, G. S. and Nikolskii, G. M.: 1961, Soviet Astron. - AJ 5, 31.
Jordan, C.: 1966, Monthly Notices Roy. Astron. Soc. 132, 463.
Jordan, C.: 1969, Monthly Notices Roy. Astron. Soc. 142, 501.
Kaburaki, O. and Uchida, Y.: 1971, Publ. Astron. Soc. Japan 23, 405.
Kakinuma, T. and Swarup, G.: 1962, Astrophys. J. 136, 975.
Kawabata, K.: 1960, Publ. Astron. Soc. Japan 12, 512.
Kopp, R. A.: 1972, Solar Phys. 27, 373.
Korol'kov, D. V. and Soboleva, N. S.: 1962, Soviet Astron. - AJ 5, 491.
Krieger, A. S., Vaiana, G. S., and Van Speybroeck, L. P.: 1971 in R. Howard (ed.); ‘Solar Magnetic Fields’, IAU Symp. 43, 397.
Kulsrud, R. M.: 1955, Astrophys. J. 121, 461.
Kuperus, M.: 1969, Space Sci. Rev. 9, 713.
Nakagawa, Y. and Raadu, M. A.: 1972, Solar Phys. 25, 127.
Nakagawa, Y., Raadu, M. A., and Harvey, J. W.: 1973a, Solar Phys. 30, 421.
Nakagawa, Y., Priest, E. R., and Wellck, R. E.: 1973b, Astrophys. J. 184, 931.
Neupert, W. M.: 1967, Solar Phys. 2, 294.
Neupert, W. M., Thomas, R. J., and Chapman, R. D.: 1974, Solar Phys. 34, 349.
Noyes, R. W., Withbroe, G. L., and Kirschner, R. P.: 1970, Solar Phys. 11, 388.
Osterbrock, D. E.: 1961, Astrophys. J. 134, 347.
Parkinson, J. H.: 1973, Solar Phys. 28, 487.
Pneuman, G. W.: 1972, Astrophys. J. 177, 793.
Rust, D. M., Nakagawa, Y., and Neupert, W. M.: 1975, Solar Phys. 41, 397.
Tousey, R., Bartoe, J.-D. F., Bohlin, J. D., Brueckner, G. E., Purcell, J. D., Scherrer, V. E., Sheeley, Jr., N. R., Schmacker, R. J., and Vanhoosier, M. E.: 1973, Solar Phys. 33, 265.
Tucker, W. H.: 1973, Astrophys. J. 186, 285.
Uchida, Y.: 1963, Publ. Astron. Soc. Japan 15, 376.
Uchida, Y. and Kaburaki, O.: 1974, Solar Phys. 35, 451.
Vaiana, G. S., Reidy, W. P., Zehnpfenning, T., Van Speybroeck, L., and Giacconi, R.: 1968, Science 161, 564.
Vaiana, G. S., Krieger, A. S., and Timothy, A. F.: 1973, Solar Phys. 32, 81.
Van Regemorter, H.: 1962, Astrophys. J. 136, 906.
Walker, A. B. C., Rugge, H. R., and Weiss, K.: 1974, Astrophys. J. 188, 423.
Wentzel, D. G.: 1974, Solar Phys. 39, 129.
White, O. R.: 1962, ‘The Center to Limb Variation of the Hα, H\ and Hγ Lines in the Solar Spectrum’, Ph.D. dissertation, Univ. of Colorado.
Widing, K. G. and Sandlin, G. D.: 1968, Astrophys. J. 152, 545.
Wittman, A.: 1973, Solar Phys. 29, 333.
Author information
Authors and Affiliations
Additional information
The National Center for Atmospheric Research is sponsored by the National Science Foundation.
Rights and permissions
About this article
Cite this article
Neupert, W.M., Nakagawa, Y. & Rust, D.M. Energy balance in a magnetically confined coronal structure observed by OSO-7. Sol Phys 43, 359–376 (1975). https://doi.org/10.1007/BF00152360
Received:
Issue Date:
DOI: https://doi.org/10.1007/BF00152360