Sunspots are known to be strong absorbers of solar oscillation modal power. The most convincing way to demonstrate this is done via Fourier–Hankel decomposition (FHD), where the local oscillation field is separated into in- and outgoing waves, showing the reduction in power. Due to the Helioseismic and Magnetic Imager’s high-cadence Doppler measurements, power absorption can be investigated at frequencies beyond the acoustic cutoff frequency. We perform an FHD on five sunspot regions and two quiet-Sun control regions and study the resulting absorption spectra α _ℓ (ν), specifically at frequencies ν > 5.3 mHz. We observe an unreported high-frequency absorption feature, which only appears in the presence of a sunspot. This feature is confined to phase speeds of one-skip waves whose origins coincide with the sunspot’s center, with v _ph = 85.7 km s⁻¹ in this case. By employing a fit to the absorption spectra at a constant phase speed, we find that the peak absorption strength lies between 0.166 and 0.222 at a noise level of about 0.009 (5%). The well-known absorption along ridges at lower frequencies can reach up to . Thus our finding in the absorption spectrum is weaker, but nevertheless significant. From first considerations regarding the energy budget of high-frequency waves, this observation can likely be explained by the reduction of emissivity within the sunspot. We derive a simple relation between emissivity and absorption. We conclude that sunspots yield a wave power absorption signature (for certain phase speeds only), which may help in understanding the effect of strong magnetic fields on convection and source excitation and potentially in understanding the general sunspot subsurface structure.

众所周知，太阳黑子是太阳振荡模态功率的强吸收体。证明这一点的最有说服力的方法是通过傅立叶-汉克尔分解 (FHD) 完成，其中本地振荡场被分成输入波和输出波，显示功率降低。由于日震和磁成像仪的高节奏多普勒测量，可以在超过声学截止频率的频率下研究功率吸收。我们对五个太阳黑子区域和两个安静的太阳控制区域执行 FHD，并研究由此产生的吸收光谱α _ℓ ( ν )，特别是在频率ν > 5.3 兆赫兹。我们观察到一个未报告的高频吸收特征，该特征仅在存在太阳黑子时出现。这一特征仅限于起源与太阳黑子中心重合的单跳跃波的相速度，在这种情况下，v _ph = 85.7 km s ^-1。通过在恒定相位速度下对吸收光谱进行拟合，我们发现峰值吸收强度介于 0.166 和 0.222 之间，噪声水平约为 0.009 (5%)。众所周知，在较低频率下沿脊的吸收可以达到. 因此，我们在吸收光谱中的发现较弱，但仍然很重要。从关于高频波的能量收支的最初考虑来看，这一观察结果很可能可以通过太阳黑子内发射率的降低来解释。我们推导出发射率和吸收率之间的简单关系。我们得出结论，太阳黑子产生波功率吸收特征（仅针对某些相速度），这可能有助于理解强磁场对对流和源激发的影响，并可能有助于理解一般的太阳黑子地下结构。