平均超颗粒的强度对比
Intensity contrast of the average supergranule
摘要：
虽然超颗粒的速度波动在太阳表面的太阳对流光谱中占主导地位，但对超颗粒尺度下的温度或密度等其他物理量的波动知之甚少。利用SDO/HMI观测，我们描述了太阳表面超颗粒的强度对比。我们确定的位置${\sim}10^4$流出和流入区域在超颗粒尺度，从我们构建的平均流量图和共同对齐的强度和磁场地图。在平均流出中心，最大强度对比度为$(7.8\pm0.6)\times10^{-4}$（视线磁场中无相应特征）。这对应于约$1.1\pm0.1$ K的温度扰动，与先前的研究一致。我们发现了一个东西各向异性，稍深的强度最小值以东的外流中心。这种演变在时间上是不对称的：在参考时间（最大流出时间）之前8小时，强度过剩较大，而在参考时间之后8小时，强度过剩几乎消失。在平均流入区域，强度对比度主要遵循磁场分布，除了东-西各向异性分量占主导地位的参考时间前8小时。我们认为强度的东西向各向异性与超颗粒的波动性质有关。
英文摘要：
While the velocity fluctuations of supergranulation dominate the spectrum of solar convection at the solar surface, very little is known about the fluctuations in other physical quantities like temperature or density at supergranulation scale. Using SDO/HMI observations, we characterize the intensity contrast of solar supergranulation at the solar surface. We identify the positions of ${\sim}10^4$ outflow and inflow regions at supergranulation scales, from which we construct average flow maps and co-aligned intensity and magnetic field maps. In the average outflow center, the maximum intensity contrast is $(7.8\pm0.6)\times10^{-4}$ (there is no corresponding feature in the line-of-sight magnetic field). This corresponds to a temperature perturbation of about $1.1\pm0.1$ K, in agreement with previous studies. We discover an east-west anisotropy, with a slightly deeper intensity minimum east of the outflow center. The evolution is asymmetric in time: the intensity excess is larger 8 hours before the reference time (the time of maximum outflow), while it has almost disappeared 8 hours after the reference time. In the average inflow region, the intensity contrast mostly follows the magnetic field distribution, except for an east-west anisotropic component that dominates 8 hours before the reference time. We suggest that the east-west anisotropy in the intensity is related to the wave-like properties of supergranulation.
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