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首页> 外文期刊>Space Science Reviews >Helioseismology of Sunspots: A Case Study of NOAA Region 9787
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Helioseismology of Sunspots: A Case Study of NOAA Region 9787

机译：黑子的太阳地震学：以美国国家海洋与大气管理局9787号地区为例

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Various methods of helioseismology are used to study the subsurface properties of the sunspot in NOAA Active Region 9787. This sunspot was chosen because it is axisymmetric, shows little evolution during 20-28 January 2002, and was observed continuously by the MDI/SOHO instrument. AR 9787 is visible on helioseismic maps of the farside of the Sun from 15 January, i.e. days before it crossed the East limb. Oscillations have reduced amplitudes in the sunspot at all frequencies, whereas a region of enhanced acoustic power above 5.5 mHz (above the quiet-Sun acoustic cutoff) is seen outside the sunspot and the plage region. This enhanced acoustic power has been suggested to be caused by the conversion of acoustic waves into magneto-acoustic waves that are refracted back into the interior and re-emerge as acoustic waves in the quiet Sun. Observations show that the sunspot absorbs a significant fraction of the incoming p and f modes around 3 mHz. A numerical simulation of MHD wave propagation through a simple model of AR 9787 confirmed that wave absorption is likely to be due to the partial conversion of incoming waves into magneto-acoustic waves that propagate down the sunspot. Wave travel times and mode frequencies are affected by the sunspot. In most cases, wave packets that propagate through the sunspot have reduced travel times. At short travel distances, however, the sign of the travel-time shifts appears to depend sensitively on how the data are processed and, in particular, on filtering in frequency-wavenumber space. We carry out two linear inversions for wave speed: one using travel-times and phase-speed filters and the other one using mode frequencies from ring analysis. These two inversions give subsurface wave-speed profiles with opposite signs and different amplitudes. The travel-time measurements also imply different subsurface flow patterns in the surface layer depending on the filtering procedure that is used. Current sensitivity kernels are unable to reconcile these measurements, perhaps because they rely on imperfect models of the power spectrum of solar oscillations. We present a linear inversion for flows of ridge-filtered travel times. This inversion shows a horizontal outflow in the upper 4 Mm that is consistent with the moat flow deduced from the surface motion of moving magnetic features. From this study of AR 9787, we conclude that we are currently unable to provide a unified description of the subsurface structure and dynamics of the sunspot.
机译：使用多种地震学方法研究了NOAA活动区9787中黑子的地下性质。之所以选择该黑子，是因为它是轴对称的，在2002年1月20日至28日期间几乎没有演化，并被MDI / SOHO仪器连续观测到。从1月15日开始，即在太阳穿过东肢之前的几天，在太阳远端的风震地图上可以看到AR 9787。在所有频率下，振荡都降低了黑子的振幅，而在黑子和斑块区域之外则看到了一个高于5.5 mHz的增强声功率区域（在安静的太阳声截止点以上）。有人认为，这种增强的声功率是由声波转换成磁声波引起的，磁声波被折射回室内并作为声波重新出现在安静的太阳下。观测表明，黑子吸收了3 mHz附近进入的p和f模式的很大一部分。通过AR 9787的简单模型对MHD波传播进行的数值模拟证实，波吸收很可能是由于入射波部分转换为沿黑子传播的磁声波。波传播时间和模式频率受太阳黑子影响。在大多数情况下，通过黑子传播的波包减少了传播时间。然而，在短距离行驶时，行驶时间偏移的迹象似乎敏感地取决于如何处理数据，尤其取决于频率-波数空间中的滤波。我们对波速进行了两种线性反演：一种使用行进时间和相速度滤波器，另一种使用来自振铃分析的模式频率。这两个反演给出了具有相反符号和不同振幅的地下波速剖面。行程时间测量还暗示了表层中不同的地下流动模式，这取决于所使用的过滤程序。当前灵敏度内核无法协调这些测量，可能是因为它们依赖于不完美的太阳振荡功率谱模型。我们提出了对经脊滤波的旅行时间流进行线性反演的方法。这种反演显示出上部4 Mm的水平流出，这与从移动磁特征的表面运动推导出的the沟流量一致。根据对AR 9787的研究，我们得出结论，我们目前无法对黑子的地下结构和动力学提供统一的描述。

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