利用GOLF/SoHO实验研究太阳粒化运动随高度的变化
Variations of the solar granulation motions with height using the GOLF/SoHO experiment
摘要：
低于1兆赫，日震速度测量的功率谱主要是对流运动（颗粒和超颗粒）的频谱，使其难以检测低阶声学模式和重力模式。我们希望更好地了解太阳颗粒化的行为作为太阳大气层中观测高度的函数，并在太阳活动周期23期间进行磁活动。利用Harvey模型分析了11年GOLF/SOHO速度-时间序列的功率谱密度（PSD），以表征太阳振荡功率谱中对流运动的性质。然后，我们研究了颗粒随太阳大气高度和太阳活动的演化。首先，我们表明，传统的使用洛仑兹配置文件，以适应包络的p模式是不太适合GOLF数据。事实上，为了正确地模拟太阳光谱，我们需要第二个洛伦兹轮廓。其次，我们表明，颗粒清楚地演变与光球的高度，但不存在任何显着的变化与活动周期。
英文摘要：
Below 1 mHz, the power spectrum of helioseismic velocity measurements is dominated by the spectrum of convective motions (granulation and supergranulation) making it difficult to detect the low-order acoustic modes and the gravity modes. We want to better understand the behavior of solar granulation as a function of the observing height in the solar atmosphere and with magnetic activity during solar cycle 23. We analyze the Power Spectral Density (PSD) of eleven years of GOLF/SOHO velocity-time series using a Harvey-type model to characterize the properties of the convective motions in the solar oscillation power spectrum. We study then the evolution of the granulation with the altitude in the solar atmosphere and with the solar activity. First, we show that the traditional use of a lorentzian profile to fit the envelope of the p modes is not well suitable for GOLF data. Indeed, to properly model the solar spectrum, we need a second lorentzian profile. Second, we show that the granulation clearly evolves with the height in the photosphere but does not present any significant variation with the activity cycle.
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