Abstract
The 20 August 1992 flare around 14:28 UT was observed in Hα, Hε and Ca ii H with the imaging spectrographs at Locarno-Monti, Switzerland, with the radiotelescopes in Bern, and in soft and hard X-rays by the Yohkoh satellite. In this paper we discuss the analysis of the temporal and spatial evolution of this flare, well observed at chromospheric and coronal layers. We find that the chromospheric electron density shows well-correlated rises with the hard X-rays emphasizing the direct response of the chromosphere to the energy deposition. Although both footpoints of the loops show simultaneous rises of the electron density, non-thermal electron injection is only observed in one of the footpoints, while an additional heating mechanism, like thermal conduction, must be assumed for the other footpoint. However, it is puzzling that all the chromospheric observations in both footpoints are delayed by ≈ 3 s compared to the hard X-ray light curve. Although this would be compatible with the thermal heating of one footpoint, it is in contradiction to the non-thermal heating of the other one. Finally, we observed evidence that during the first part of the flare a thermal conduction front propagates at a speed of ≈ 2000 km s-1 into a second loop, in which the energy release occurs in the second part of the flare.
This is a preview of subscription content, log in via an institution to check access.
Similar content being viewed by others
References
de la Beaujardière, J.-F., Canfield, R. C., Hudson, H. S., Wülser, J.-P., Acton, L., Kosugi, T., and Masuda, S.: 1995, Astrophys. J. 440, 386.
Canfield, R. C., Zarro, D. M., Metcalf, T. R., and Lemen, J. R.: 1990, Astrophys. J. 348, 333.
Falchi, A., Falciani, R., and Smaldone, L. A.: 1992, Astron. Astrophys. 256, 255.
Fisher, G. H.: 1989, Astrophys. J. 346, 1019.
Graeter, M.: 1990, Solar Phys. 130, 337.
Graeter, M.: 1993, Astron. Astrophys. Suppl. Series 98, 261.
Graeter, M. and Kucera, T. A.: 1992, Solar Phys. 141, 91.
Griem, H. R.: 1962, Astrophys. J. 136, 422.
Kämpfer, N. and Schöchlin, W.: 1982, Astrophys. J. 78, 215.
Kosugi, T., Makishima, K., Murakami, T., Sakao, T., Dotani, T., Inda, M. et al.: 1991, Solar Phys. 136, 17.
Marti, A.: 1993, Diploma Thesis, Institute of Applied Physics, University of Bern, Switzerland.
Masuda, S.: 1994, ‘Hard X-ray Sources and the Primary Energy Release Site in Solar Flares’, PhD thesis, University of Tokyo, Tokyo.
Masuda, S., Kosugi, T., Tsuneta, S., and Hara, H.: 1996, Adv. Space Res. 17(4–5), 63.
Metcalf, T. R., Hudson, H. S., Kosugi, T., Puetter, R. C., and Piña, R. K.: 1996, Astrophys. J. 466, 585.
Neidig, D. F., Kiplinger, A. L., Cohl, H. S., and Wiborg, P.H.: 1993, Astrophys. J. 406, 306.
Ogawara, Y., Takano, T., Kato, T., Kosugi, T., Tsuneta, S., Watanabe, T., Kondo, I., and Uchida, Y.: 1991, Solar Phys. 136, 1.
Rolli, E. and Magun, A.: 1995, Solar Phys. 160, 29.
Rolli, E., Wülser, J.-P., and Magun, A.: 1998, Solar Phys. 180, 343 (this issue).
Sakao, T.: 1994, ‘Characteristics of Solar Flare Hard X-ray Sources as Revealed with the Hard X-ray Telescope aboard the Yohkoh Satellite’, PhD thesis, University of Tokyo, Tokyo.
Sakao, T., Kosugi, T., Masuda, S., Yaji, K., Inda-koide, M., and Makishima, K.: 1996, Adv. Space Res. 17(4–5), 67.
Tsuneta, S., Acton, L., Bruner, M., Lemen, J., Brown, W., Caravalho, R. et al.: 1991, Solar Phys. 136, 37.
Wülser, J.-P. and Marti, H.: 1989, Astrophys. J. 341, 1088.
Wülser, J.-P., Canfield, R. C., Acton, L. W., Culhane, J. L., Phillips, A., Fludra, A., Sakao, T., Masuda, S., Kosugi, T., and Tsuneta, S.: 1994, Astrophys. J. 424, 459.
Author information
Authors and Affiliations
Rights and permissions
About this article
Cite this article
Rolli, E., Wülser, J.P. & Magun, A. Multiwavelength Flare Observations: Temporal Evolution of the 20 August 1992 Flare. Solar Physics 180, 361–375 (1998). https://doi.org/10.1023/A:1005022327027
Issue Date:
DOI: https://doi.org/10.1023/A:1005022327027