1974年10月11日太阳耀斑金属线的不对称性和线心位移

ASYMMETRY AND DOPPLER SHIFT OF THE METALLIC LINES OF THE SOLAR FLARE ON 11 OCTOBER 1974

分析了１９７４年１０月１１日ＩＮ级耀斑金属线的不对称性和线心位移。结果发现：不对称性极大发生在线心强度极大之前；具有红不对称性的谱线约占５０％，蓝不对称性的谱线约占２０％．其余的谱线，不对称性不明显；不管是哪一种不对称性，其线心位移都较小，总体上表现为微弱的蓝移。这些结果非常有助于深入了解太阳耀斑低层大气的动力学过程。本文认为，由耀斑爆发而引起的温度极小区附近物质的运动过程可基本解释这些观测现象。

On 11 October 1974 an 1N flare occurred near the solar disk center (N12E02) at 03: 25 UT. A 25 cm coronagraph at the Norikura station of the National Astronomical Observatory of Japan was used to do the spectral and photographic observations. The diameter of the solar image is 81 mm. The spectrum has a wavelength range of 3590～ 3990 and a linear dispersion of 1. 16 mm-1. The exposure time is 0. 1～0. 2s. The observations were made from 03: 27UT to 03: 40UT. Eleven frames of spectrum were obtained during the flare. Our analysis concerns only 6 typical frames which were chosen according to the quality of spectra; they contain basically main developing stages of the flare. The flare is a white-light flare(WLF), as can be seen in Figure 1 and Figure 2. There are a pronounced continuum emission and many metallic lines appeared at two flaring bright kernels. Using a PDS microdensitometer at the Astronomical Institute of Tokyo University, we scanned the spectograms at the brightest flare kernel and at the nearby undisturbed photospheric region. The digitized data were analysed by use of IRAF software from Kitt Peak Observatory on a Sun4/280 computer. A series of 'continuum windows'have been chosen at fbi, where the intensities are local maxima and, especially, around fi both the intensity profiles o f the flare and the near undisturbed, photospheric region have similar forms. It was assumed that at these wavelength points, the ratio between the flare intensity and the photopheric intensity is equal to the ratio between the intensities of the flare 'real' continuum and the photosphere continuum. Every line profile has been imitated with Gauss profile and, its line center was chosen as the areals line center. Doppler shift difference between the flare line and the nearby quiet photospheric region line was defined as where Δλ0 is the average wavelength difference between the wavelength-points at the 'continuum windows' of the flare spectrum and of the nearby quiet photospheric region, λf, λq is the wavelength of the flare line center and that of the line center of the quiet region respectively. In this paper, the asymmetries and the Doppler shifts of the 41 metallic lines of the flare are analysed in detail. The results indicate: (1) The maximum of the asymmetry precedes the maximum of the intensity at the line center; (2) About 50% of lines show red asymmetry, while blue asymmetry appears in 20% of lines, the rest does not show obvious asymmetry; (3) The line always has no obvious shift regardless of the line asymmetry, probably showing a small blue shift as a whole. These results are helpful to understand the dynamic process in the lower atmosphere of solar flares. It is proposed that the movements around the temperature minimum region caused by the flare could explain these observational results.