Abstract
The Solar Maximum Mission Satellite, the Sacramento Peak Vacuum Tower Telescope, the Very Large Array and the Westerbork Synthesis Radio Telescope have been used to observe active region AR 2490 on two consecutive days at soft X-ray, ultraviolet, optical and radio wavelengths (2, 6, and 20 cm), with comparable angular resolution (2″ to 15″) and field of view (4′ × 4′). The radio emissions at λ = 6 cm and 20 cm show a double structure in which one component is associated with bright Hα plage, C iv and soft X-ray emission, and the other component is associated only with sunspots. No radiation at λ = 2 cm is detected in this latter component. Coronal temperature and emission measure derived from X-ray lines indicate that the dominant radiation mechanism of the plage-associated component is due to thermal bremsstrahlung while the gyroresonance absorption coefficient must be invoked to account for the high brightness temperature (T b ≈2×106K) observed in the sunspot associated component. The high magnetic field strength needed (600 G at a level where T∼2×106K) is explained assuming a thin transition zone, in order to reach a high electron temperature close to the sunspot, where the magnetic fields are stronger. A higher temperature gradient above sunspots is also consistent with the absence of detectable C iv emission.
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., Culhane, J. L., Gabriel, A. H., Bentley, R. D., Bowles, J. A., Firth, J. G., Finch, M.L., Gilbreth, C. W., Guttridge, P., Hayes, R. W., Joki, E. G., Jones, B. B., Kent, B. J., Leibacher, J. W., Nobles, R. A., Patrick, T. J., Phillips, K. J. H., Rapley, C. G., Sheathev, P. H., Sherman, J. C., Stark, J. P., Springer, L. A., Turner, R. F., and Wolfson, C. J.: 1980, Solar Phys. 65, 53.
Alissandrakis, C. E., Kundu, M. R., and Lantos, P.: 1980, Astron. Astrophys. 82, 30.
Baars, J. W., Genzel, R., Pauliny-Toth, I. I. K., and Witzel, A.: 1977, Astron. Astrophys. 61, 99.
Bandiera, R.: 1982, Astron. Astrophys., (in press).
Bromboszcz, G., Jakimiec, J., Siarkowski, M., Sylwester, B., Sylwester, J., Obridko, V., Fürstenberg, F., Hildebrandt, J., Krüger, A., and Staude, J.: 1982, Proceedings of the SMY Workshop, Crimea, March 23–29, 1981.
Chiuderi, C., Chiuderi-Drago, F., and Noci, G.: 1971, Solar Phys. 17, 369.
Felli, M., Lang, K. R., and Willson, R. F.: 1981, Astrophys. J. 247, 325.
Gelfreikh, G. B., Makarov, V. I., Mikhailutea, V. P., Korzhavin, A. N., and Rybkina, G. B.: 1981, ‘Simultaneous Optical and Radio Observations of a Corona Condensation Off the Limb on November 19, 1980’, preprint.
Kakinuma, T. and Swarup, G.: 1962, Astrophys. J. 136, 975.
Kundu, M.R., Alissandrakis, C. E., Bregman, J. D., and Hin, A. C.: 1977, Astrophys. J. 213, 278.
Kundu, M. R., Schmahl, E. J., and Gerassimenko, M.: 1980, Astron. Astrophys. 82, 265.
Kundu, M. R., Schmahl, E. J., and Rao, A. P.: 1981, Astron. Astrophys. 94, 72.
Lang, K. R. and Willson, R. F.: 1979, Nature 278, 24.
Lang, K. R. and Willson, R. F.: 1980, in M. R. Kundu and T. E. Gergely (eds.), ‘Radio Physics of the Sun’, IAU Symp. 89, 109.
Pallavicini, R., Vaiana, G. S., Tofani, G., and Felli, M.: 1979, Astrophys. J. 229, 375.
Pallavicini, R., Sakurai, T., and Vaiana, G. S.: 1981, Astron. Astrophys., (in press).
Ratcliffe, J. A.: 1959, The Magneto-Ionic Theory, Cambridge University Press, Cambridge.
Author information
Authors and Affiliations
Additional information
Cooperative study of the SMY-FBS Project.
On leave from the University of Napoli.
On leave from the University of Torino.
On sabbatical leave 1980–81 at the Arcetri Observatory.
On leave from Toyokawa Observatory, Japan.
Rights and permissions
About this article
Cite this article
Chiuderi-Drago, F., Bandiera, R., Falciani, R. et al. Multiple wavelength observations of a solar active region. Sol Phys 80, 71–85 (1982). https://doi.org/10.1007/BF00153424
Received:
Revised:
Issue Date:
DOI: https://doi.org/10.1007/BF00153424