局部压制波源对日震走时的影响
Impact of Locally Suppressed Wave sources on helioseismic travel times
摘要：
太阳黑子附近的波走时偏移通常被解释为主要由磁场、流动和声速的局部变化引起。我们在这里表明，在太阳黑子的颗粒相关的波源的抑制也可以显着地有助于这些旅行时间的变化，在某些情况下，在和传出波的旅行时间之间的不对称。旅行时的物理解释和源分布均匀性之间的紧密联系得到证实。统计上显着的走时偏移恢复后，数值模拟波传播的存在下，在本地化的源强度下降。我们还表明，这些时间偏移是相对敏感的模态阻尼率，因此，我们只能把这种效果的大小上的界限。我们看到在短距离（$\sim 6.2$ Mm）处$p$模式平均传播时间系统地减少了10-15秒，这可能被误解为由声速的浅（1.5 Mm的厚度）增加（$\sim$ 4%）引起。在较大的传播距离（$\sim 24$ Mm）处，观察到传入和传出波传播时间之间的6-13 s差异;这可能被错误地解释为由流动引起。
英文摘要：
Wave travel-time shifts in the vicinity of sunspots are typically interpreted as arising predominantly from magnetic fields, flows, and local changes in sound speed. We show here that the suppression of granulation related wave sources in a sunspot can also contribute significantly to these travel-time shifts, and in some cases, an asymmetry between in and outgoing wave travel times. The tight connection between the physical interpretation of travel times and source-distribution homogeneity is confirmed. Statistically significant travel-time shifts are recovered upon numerically simulating wave propagation in the presence of a localized decrease in source strength. We also demonstrate that these time shifts are relatively sensitive to the modal damping rates; thus we are only able to place bounds on the magnitude of this effect. We see a systematic reduction of 10-15 seconds in $p$-mode mean travel times at short distances ($\sim 6.2$ Mm) that could be misinterpreted as arising from a shallow (thickness of 1.5 Mm) increase ($\sim$ 4%) in the sound speed. At larger travel distances ($\sim 24$ Mm) a 6-13 s difference between the ingoing and outgoing wave travel times is observed; this could mistakenly be interpreted as being caused by flows.
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