Abstract
Several solar flares have been observed from their onset in C IV λ 1548.2 and 1–8 Å X-rays using instruments aboard OSO-8. In addition, microwave and Hα flare patrol data have been obtained for this study. The impulsive brightening in C IV is frequently accompanied by redshifts, interpreted as downflows, of the order of 80 km s-1. The maximum soft X-ray intensity usually arrives several minutes after the maximum C IV intensity. The most energetic C IV event studied shows a small blueshift just before reaching maximum intensity, and estimates of the mass flux associated with this upflow through the transition-zone are consistent with the increase of mass in the coronal loops as observed in soft X-rays. This event had no observable microwave burst, suggesting that electron beams did not play a major role in the chromospheric and transition-zone excitation. Lastly, our observations suggest that the frequent occurrence of violent dynamical processes at the onset of the flare are associated with the initial energy release mechanism.
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Currently at High Altitude Observatory, National Center for Atmospheric Research, P.O. Box 3000, Boulder, Colo. 80307, U.S.A.
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Lites, B.W., Bruner, E.C. & Wolfson, C.J. OSO-8 observations of the impulsive phase of solar flares in the transition-zone and corona. Sol Phys 69, 373–389 (1981). https://doi.org/10.1007/BF00150001
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DOI: https://doi.org/10.1007/BF00150001