太阳黑子本影大气半经验模型

A SEMI-EMPIRICAL MODEL OF SUNSPOT UMBRA

本文利用美国Kitt峰天文台McMath太阳塔13.5米光谱仪观测到的1985年7月1日太阳黑子光谱资料(包括H_α,H_β,CaIIH,K,λ8498,λ8542及λ8662七条谱线),通过非局部热动平衡计算,建立了黑子本影新的半经验模型.计算结果表明,本影在色球上层的温度比宁静太阳和半影均高,这同以往模型的结果在定性上是一致的.色球层的温度分布以"平台"结构为特征,但"平台"的宽度比以往模型要窄.在光球层,微观湍动速度较以往模型要小.黑子大气中不存在辐射平衡,在温度极小区,辐射损失出现负值.

Based on the profiles of H_α, H_β, CaIIH, K and infrared lines observed with the 13.5 meter vacuum spectrometer of the McMath telescope at Kitt Peak Observatory on July 1, 1985, a semiempirical model of sunspot umbra is presented in this paper. Non-LTE calculations for the umbral atmosphere have been carried out by solving the hydrostatic, statistical equilibrium and radiative transfer equations iteratively. The optimum model reproducing the observed spectra well is derived using trial and error method. The main features of this umbral model can be illustrated as follows: (1) the temperature structure of the corona and transition region is similar to the VAL3C quiet Sun model; (2) the chromospheric structure is characterized by a temperature plateau, with a higher temperature than the penumbral model in the upper layers; (3) the minimum temperature is 3130 K and about 300 K less than that in the penumbral model; (4) the temperature structure of the photosphere is not significantly different from those in the former umbral models by other authors, while the micro-turbulent velocity is somewhat less than the usual values. By computations we find that there is no radiative balance in the whole atmosphere. The net radiative loss rate has a maximum in the middle chromosphere, while the value is negative in the temperature minimum region.