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Observations of the Caxixresonance line during the impulsive phase of solar flares

✍ Scribed by K. G. McClements; D. Alexander

Publisher: Springer
Year: 1989
Tongue: English
Weight: 909 KB
Volume: 123
Category: Article
ISSN: 0038-0938
DOI: 10.1007/bf00150018

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✦ Synopsis

Numerical simulations of flaring coronal loops, based on the assumption of an electron beam energy input, show that material is ablated from the chromosphere at approximately the local sound speed, thus giving rise to an overall blueshift in the spectrum of the soft X-ray Ca xIx resonance line of up to 5 m]~. In this paper we critically examine the observational evidence for the existence of this blueshift. From an exhaustive analysis of seven limb flares and nine disk flares, we find no indication of CaxIx blueshifts in excess of about 1 m,~. This conclusion may present serious problems for the electron beam hypothesis: possible reasons for the apparent discrepancy between theory and observations are discussed.

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