The impulsive and gradual phases of a solar limb flare as observed from the solar maximum mission satellite
β Scribed by A. I. Poland; M. E. Machado; C. J. Wolfson; K. J. Frost; B. E. Woodgate; R. A. Shine; P. J. Kenny; C. C. Cheng; E. A. Tandberg-Hanssen; E. C. Bruner; W. Henze
- Publisher
- Springer
- Year
- 1982
- Tongue
- English
- Weight
- 732 KB
- Volume
- 78
- Category
- Article
- ISSN
- 0038-0938
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β¦ Synopsis
Simultaneous observations of a solar limb flare in the X-ray and ultraviolet regions of the spectrum are presented. Temporal and spectral X-ray observations were obtained for the 25-300 keV range while temporal, spectral, and spatial X-ray observations were obtained for the 30-0.3 keV range. The ultraviolet observations were images with a 10" spatial resolution in the lines ofO v (T e ~ 2.5 β’ 105 K) and Fe xxI (T e ~ 1.1 β’ 107 K). The hard X-ray and O v data indicate that the impulsive phase began in the photosphere or chromosphere and continued for several minutes as material was ejected into the corona. Impulsive excitation was observed up to 30 000 km above the solar surface at specific points in the flare loop. The Fe xxI observations indicate a preheating before the impulsive phase and showed the formation of hot post-flare loops. This later formation was confi!'med by soft X-ray observations. These observations provide limitations for current flare models and will provide the data needed for initial conditions in modeling the concurrent coronal transient.
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The properties and development of a high-temperature current sheet characterized by increasing merging velocity are studied and related to the early phases of solar flares. It is shown that the system can be described by the Petschek-type geometry for a wide range of merging velocities. In the diffu