A two-temperature model for the flare of 5 September, 1973

✍ Scribed by Irene R. Little-Marenin; J. K. Silk; A. S. Krieger

• Book ID: 104644864
• Publisher: Springer
• Year: 1980
• Tongue: English
• Weight: 818 KB
• Volume: 65
• Category: Article
• ISSN: 0038-0938
• DOI: 10.1007/bf00152796

✦ Synopsis

The energetics and mass transfer during the X-ray flare of 18:31 GMT on 5 September, 1973 have been studied using the observations in the objective grating mode of the AS&E X-ray spectrographic telescope on Skylab. The flare was a moderately energetic one, Class M1 according to Solrad. In Ha, however, it was only a subflare of class -N. The data are approximately monochromatic images of the small X-ray source. They show a continued rise in the emission for several minutes followed by a decline. The size and temporal evolution are slightly different for ions associated with higher temperatures (Fe xxII, Si XIII) than with those of lower temperatures (Fe xvII, Mg xI). The time of maximum emission moves from one side of the flare to the other and peaks earlier for hotter temperature ions. The observations are analyzed using a two-temperature model in order to determine the changes in the distribution of emission measure and of the amount of material as a function of temperature. The development of the flare can be divided into three periods in each of which different mechanisms are operating. For the first 3-4 min, evaporation drives mass into the entire emitting region. Second, the evaporation ceases: Hot material loses energy, and we see a loss of hot material and a corresponding gain of cool material. Later, after 18:38, we see a decline in the emission measure. spots flanking the neutral line, making this flare an example of the class of 'double ribbon' flares.

Microwave and type III emission indicated that the flare had an impulsive component. The type III onset occurred just before or at the time of first brightening in Ha, the microwave burst onset followed the Ha and soft X-ray onsets, and the peak of the impulsive burst occurred about 2 min before the Ha and soft X-ray peak.