The super-hot thermal component in the decay phase of solar flares

✍ Scribed by Hua-An Lin; R. P. Lin; S. R. Kane

• Publisher: Springer
• Year: 1985
• Tongue: English
• Weight: 693 KB
• Volume: 99
• Category: Article
• ISSN: 0038-0938
• DOI: 10.1007/bf00157311

✦ Synopsis

Solar X-ray observations from balloons and from the SMM and HINOTORI spacecraft have revealed evidence for a super-hot thermal component with a temperature of > 3 • 107K in many solar flares, in addition to the usual 10-20 • 106 K soft X-ray flare plasma. We have systematically studied the decay phase of 35 solar flare X-ray events observed by ISEE-3 during 1980. Based on fits to the continuum X-ray spectrum in the 4.8-14 keV range and to the intensity of the 1.9 A feature of iron lines, we find that 15 (about 43 %) of the analyzed events have a super-hot thermal component in the decay phase of the flare. In this paper the important properties of the super-hot thermal component in the decay phase are summarized. It is found that an additional input of energy is required to maintain the super-hot thermal components. Finally, it is suggested that the super-hot thermal component in the decay phase is created through the reconnection of the magnetic field during the decay phase of solar flares.

Recently, a new component whose X-ray spectrum includes both soft (< 15 keV) X-rays and hard (> 15 keV) X-rays has been identified in solar flares. From an intense flare on June 27, 1980, Linet aL (1981) found a near isothermal component with temperature T ~ 34 • 106 K through the measurements with a balloon-borne array of germanium detectors with very high spectral resolution (< 1 keV). At the same time, the usual 10-20 x 10 6 K soft X-ray thermal emission was also present. We call this new component the 'super-hot thermal component' (shortened to 'SHTC') to distinguish it from the usual soft X-ray thermal emission.