粒子追踪揭示的太阳超米粒现象
Solar supergranulation revealed by granule tracking
摘要：
内容：超微粒化是太阳表面速度场的一种模式，人们已经知道了50多年，然而，对于它的起源还没有令人满意的解释。目的：因此，需要新的观测约束来指导理论方法，这些方法在引起表面湍流对流的大规模不稳定性或浮力的直接强迫的情景之间犹豫不决。方法：我们使用Pic-du-Midi天文台的14-Mpixel CALAS相机，获得了一个7. 5小时长的高分辨率图像序列，具有前所未有的视场大小。跟踪颗粒，我们已经确定了在太阳表面的速度场非常详细的规模从2.5毫米到250毫米。结果：动能密度谱显示，超颗粒峰位于36 μ m处，范围在20 μ m和75 μ m之间。在小尺度下，超颗粒流的减少接近于$k^{-2}$ -幂律，比均分Kolmogorov定律更陡。发散场的概率分布函数显示了超颗粒的不稳定性的特征，因此也显示了它的湍流性质。
英文摘要：
Context: Supergranulation is a pattern of the velocity field at the surface of the Sun, which has been known about for more than fifty years, however, no satisfactory explanation of its origin has been proposed. Aims: New observational constraints are therefore needed to guide theoretical approaches which hesitate between scenarios that either invoke a large-scale instability of the surface turbulent convection or a direct forcing by buoyancy. Method: Using the 14-Mpixel CALAS camera at the Pic-du-Midi observatory, we obtained a 7.5h-long sequence of high resolution images with unprecedented field size. Tracking granules, we have determined the velocity field at the Sun's surface in great detail from a scale of 2.5Mm up to 250Mm. Results: The kinetic energy density spectrum shows that supergranulation peaks at 36Mm and spans on scales ranging between 20Mm and 75Mm. The decrease of supergranular flows in the small scales is close to a $k^{-2}$-power law, steeper than the equipartition Kolmogorov one. The probability distribution function of the divergence field shows the signature of intermittency of the supergranulation and thus its turbulent nature.
机构、总结、中文摘要均由AI分析而来，可能存在错误，请以论文正文为准。
