AI 中文总结
该研究利用时间-距离日震学研究太阳黑子内声波传播，测量进出黑子波的传播时间并建模。发现进出波传播时间均缩短且有不对称性，总体减少或因多种因素，不对称或与地下流动有关，虽模型再现部分特征，但仍有定量差异。
AI 中文摘要
绘制太阳黑子的地下结构和流场一直是日震学的一项具有挑战性的任务。在这项工作中，我们使用时间-距离日震学研究了美国国家海洋和大气管理局11312活动区中一个太阳黑子内声波的传播。测量了进出太阳黑子的波的传播时间，它是相对于局部径向方向的传播距离和方位角的函数。同样的时间-距离分析也应用于基于太阳黑子磁流体静力学（MHS）模型的模拟数据，并使用基于MHS太阳黑子模型和磁流体动力学（MHD）模拟的射线追踪对传播时间进行正演建模。我们发现，进入（从宁静区域进入太阳黑子）和离开（从太阳黑子进入宁静区域）的波的传播时间都比宁静太阳中的短，传播时间减少高达40秒。平均时间偏移量的大小对于在小传播距离上沿径向传播的波最大。在进入和离开的波之间检测到明显的不对称性：离开的波通常表现出更短的传播时间。这种不对称性在径向方向和小传播距离上最强，对于3.5 mHz和4.5 mHz的波，差异超过1分钟。从观测和模型的结果来看，我们的分析表明，传播时间的总体减少可能主要是由威尔逊凹陷、磁场和波速扰动的综合作用引起的，而进出不对称性可能部分归因于地下流动。尽管正演建模结果再现了观测的几个定性特征，但定量差异仍然存在，突出了当前太阳黑子模型和射线理论近似的局限性。
英文摘要
Mapping the subsurface structure and flow field of sunspots has been a challenging task for helioseismology. In this work, we investigate the propagation of acoustic waves in a sunspot in NOAA active region 11312 using time-distance helioseismology. Travel times of waves traveling into and out of the sunspot are measured as functions of travel distance and azimuthal angle relative to the local radial direction. The same time-distance analysis is also applied to a simulated data based on a magnetohydrostatic (MHS) model of sunspot, and forward modeling of travel times is performed using ray tracing based on both the MHS sunspot model and a magnetohydrodynamic (MHD) simulation. We find that both ingoing (traveling from the quiet area into the sunspot) and outgoing waves (traveling from the sunspot into the quiet area) have shorter travel times than in the quiet Sun, with travel-time reductions of up to 40 s. The magnitude of the mean time shift is largest for waves traveling along the radial direction at small travel distances. A clear asymmetry is detected between ingoing and outgoing waves: outgoing waves generally exhibit shorter travel times. This asymmetry is strongest for radial direction and small travel distances, with differences exceeding 1 min for 3.5 mHz and 4.5 mHz waves. From the results of both observations and models, our analysis indicates that the overall reduction in travel time could be primarily caused by the combined effects of Wilson depression, magnetic field, and wave-speed perturbations, while the ingoing-outgoing asymmetry could be partly attributable to subsurface flows. Although the forward-modeling results reproduce several qualitative features of the observations, quantitative discrepancies remain, highlighting limitations of current sunspot models and ray-theoretical approximations.
Comments17 pages, 8 figures
