Abstract
In solar flares the Yohkoh Hard X-ray Telescope (HXT) has revealed, in addition to the most prominent double-footpoint sources, several types of coronal hard X-ray sources. (1) A compact source that appears only during the impulsive phase. It is located above the soft X-ray loop and has a relatively hard spectrum. This strongly suggests that magnetic reconnection takes place above (outside of) the bright soft X-ray loop. It is maybe that the reconnection outflow impinges upon the underlying loop, forms a shock, and energized electrons resulting in a hard X-ray source above the loop. (2) A gradual source that begins in the impulsive phase but becomes dominant later in the gradual phase with a characteristic time scale of 5–10 min. It is located near the soft X-ray loop apex and is characterized by a very soft spectrum, which is interpreted as originating from an isothermal plasma with the electron temperatures of 30–40 MK. The plasma seems to be directly heated in situ to those super-hot temperatures. (3) Another gradual source seen in the so-called super-hot thermal flares (Type A flares). This source is quite similar to the gradual source mentioned above, but appears with quite weak, if any, impulsive signatures. (4) A coronal source seen in Long Duration Event (LDE) flares. LDE flares usually show a clear cusp- shaped loop structure in soft X-rays, in which a soft-spectrum, relatively large-sized (1–2 arcmin), long-lasting (typically 30 min) hard X-ray source appears. It is located below the soft X-ray cusp but slightly above the densest portion of the bright soft X-ray loop.
This is a preview of subscription content, log in via an institution to check access.
Access this chapter
Tax calculation will be finalised at checkout
Purchases are for personal use only
Preview
Unable to display preview. Download preview PDF.
References
Aschwanden, M. J., Hudson, H., Kosugi, T., and Schwartz, R. A. (1996a) Electron Time-of-Flight Measurements during the Masuda Flare, 1992 January 13, Astrophys. J., 464, pp. 985–998
Aschwanden, M. J., Wills, M. J., Hudson, H. S., Kosugi, T., and Schwartz, R. A. (1996b) Electron Time-of-Flight Distances and Flare Loop Geometries Compared from CGRO and Yohkoh Observations, Astrophys. J., 468, pp. 398–417
Aschwanden, M. J., Kosugi, T., Hudson, H. S., Wills, M. J., and Schwartz, R. A. (1996c) The Scaling Law between Electron Time-of-Flight Distances and Loop Lengths in Solar Flares, Astrophys. J., 470, pp. 1198–1217
Kosugi, T., Makishima, K., Murakami, T., Sakao, T., Dotani, T., Inda, M., Kai, K., Masuda, S., Nakajima, H., Ogawara, Y., Sawa, M., and Shibasaki, K. (1991) The Hard X-ray Telescope (HXT) for the Solar-A Mission, Solar Phys., 136, pp. 17–36
Kosugi, T., Sakao, T., Masuda, S., Hara, H., Shimizu, T., and Hudson, H. S. (1994) Hard and Soft X-ray Observations of a Super-hot Thermal Flare of 6 February, 1992, in S. Enome and T. Hirayama (eds.),”New Look at the Sun with Emphasis on Advanced Observations of Coronal Dynamics and Flares”, pp. 127–129
Lin, R. P., Schwartz, R. A., Pelling, R. M., and Hurley, K. C. (1981) A New Component of Hard X-rays in Solar Flares, Astrophys. J. Lett., 251, pp. L109-L114
Masuda, S. (1994a) Hard X-ray Sources and the Primary Energy Release Site in Solar Flares, Ph.D. Thesis, Univ. of Tokyo.
Masuda, S. (1994b) Vertical Structure of Hard X-ray Sources in Solar Flares, in S. Enome and T. Hirayama (eds.),”New Look at the Sun with Emphasis on Advanced Observations of Coronal Dynamics and Flares”, pp. 209–212
Masuda, S., Kosugi T., Hara H., Tsuneta S., and Ogawara Y. (1994) A Loop-Top Hard X-ray Source in a Compact Solar Flare as Evidence for Magnetic Reconnection, Nature, 371, pp. 495 497
Masuda, S., Kosugi T., Hara H., Sakao T., Shibata K., and Tsuneta S. (1995) Hard X-ray Sources and the Primary Energy-Release Site in Solar Flares, Publ. Astron. Soc. Japan, 47, pp. 677 689
Ogawara, Y., Takano, T., Kato, T., Kosugi, T., Tsuneta, S., Watanabe, T., Kondo, I., and Uchida, Y. (1991) The Solar-A Mission: An Overview, Solar Phys., 136, pp. 1–16
Sakao, T. (1994) Characteristics of Solar Flare Hard X-ray Sources as Revealed with the Hard X-ray Telescope aboard the Yohkoh Satellite, Ph.D. thesis, Univ. of Tokyo.
Sakao, T., Kosugi, T., Masuda, S., Yaji, K., Inda-Koide, M., and Makishima, K. (1994) Hard X-ray Imaging Observations of Footpoint Sources in Impulsive Flares, in S. Enome and T. Hirayama (eds.),”New Look at the Sun with Emphasis on Advanced Observations of Coronal Dynamics and Flares”, pp. 169–172
Shibata, K., Masuda, S., Hara, H., Yokoyama, T., Tsuneta, S., Kosugi, T., and Ogawara, Y. (1995) Hot-Plasma Ejections Associated with Compact-Loop Solar Flares, Astrophys. J., 451, L83–L85
Somov, B. V. and Kosugi, T. (1997) Collisionless Reconnection and High-Energy Particle Acceleration in Solar Flares, Astrophys. J., in press
Tanaka, K. (1987) Impact of X-Ray Observations from the Hinotori Satellite on Solar Flare Research, Publ. Astron. Soc. Japan, 39, pp. 1–45
Tsuneta, S. (1996) Structure and Dynamics of Magnetic Reconnection in a Solar Flare, Astrophys. J., 456, pp. 840–849
Tsuneta, S., Acton, L., Bruner, M., Lernen, J., Brown, W., Caravalho, R., Catura, R., Freeland, S., Jurcevich, B., Morrison, M., Ogawara, Y., Hirayama, T., Owens, J. (1991) The Soft X-ray Telescope for the Solar-A Mission, Solar Phys., 136, pp. 37–67
Tsuneta, S., Hara, H., Shimizu, T., Acton, L.W., Strong, K.T., Hudson, H.S., and Ogawara, Y. (1992) Observation of a Solar Flare at the Limb with the Yohkoh Soft X-ray Telescope, Publ. Astron. Soc. Japan, 44, pp. L63–L69.
Tsuneta, S., Masuda, S., Kosugi, T., and Sato, J. (1997) Hot and Super-Hot Plasmas above an Impulsive-Flare Loop, Astrophys. J., 478, pp. 787–798
Wang, H., Gary, D. E., Zirin, H. Kosugi, T., Schwartz, R. A., and Linford, G., (1995) The Microwave and Hα sources of the 1992 January 13 Flare, Astrophys. J. Lett., 444, pp. L115–L118
Author information
Authors and Affiliations
Editor information
Editors and Affiliations
Rights and permissions
Copyright information
© 1998 Springer Science+Business Media Dordrecht
About this chapter
Cite this chapter
Masuda, S., Kosugi, T., Sakao, T., Sato, J. (1998). Coronal Hard X-Ray Sources in Solar Flares Observed with Yohkoh/HXT. In: Watanabe, T., Kosugi, T., Sterling, A.C. (eds) Observational Plasma Astrophysics: Five Years of Yohkoh and Beyond. Astrophysics and Space Science Library, vol 229. Springer, Dordrecht. https://doi.org/10.1007/978-94-011-5220-4_42
Download citation
DOI: https://doi.org/10.1007/978-94-011-5220-4_42
Publisher Name: Springer, Dordrecht
Print ISBN: 978-94-010-6198-8
Online ISBN: 978-94-011-5220-4
eBook Packages: Springer Book Archive