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arXiv 1208.1644astro-ph.SR
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{ \it太阳动力学天文台}光球和色球观测的二维日震功率、相位和相干谱

Two-Dimensional Helioseismic Power, Phase, and Coherence Spectra of {\it Solar Dynamics Observatory} Photospheric and Chromospheric Observables

Rachel Howe, Kiran Jain, Richard S. Bogart, Deborah A. Haber, Charles S. Baldner

摘要:

虽然{\it太阳动力学天文台}(SDO)上的{\it日震和磁成像仪}(HMI)提供多普勒速度[ $V$ ]、连续强度[ $I_C$ ]和线深度[ $Ld$ ]观测,其中每一个都对五分钟的声谱敏感,{ \it大气成像阵列}(AIA)也在波长上进行观测--特别是1600和1700埃波段--这些波段部分形成于上层光球层中,并且对声学模式具有良好的灵敏度。在这篇文章中,我们考虑的时空傅立叶谱的特点,在AIA和HMI观测的15度区域周围的NOAA活动区11072。我们映射的空间-时间-功率分布为不同的可观测和HMI线核心[ $I_L$ ],或连续减去线深度,和相位和相干函数为选定的可观测对,作为位置和频率的函数。五分钟振荡功率在所有可观测的太阳黑子和斑区也被抑制。在声学截止频率以上,行为更加复杂:HMI $I_C$中的功率在存在表面磁场的情况下仍然被抑制,而HMI $I_L$和AIA带中的功率在表面场的区域中被抑制,但是在有源区周围的扩展区域中被增强,并且HMI $V$中的功率在强场集中周围的狭窄区域中被增强,并且在更宽的周围区域中被抑制。观测量的相对相位和它们的交叉相干函数也在活动区域周围改变。这些效应可能有助于我们了解光球层不同层中波和磁场的相互作用,在对活动区进行多波长局部日震分析时需要考虑这些效应。

英文摘要:

While the {\it Helioseismic and Magnetic Imager} (HMI) onboard the {\it Solar Dynamics Observatory} (SDO) provides Doppler velocity [$V$], continuum intensity [$I_C$], and line-depth [$Ld$] observations, each of which is sensitive to the five-minute acoustic spectrum, the {\it Atmospheric Imaging Array} (AIA) also observes at wavelengths -- specifically the 1600 and 1700 Angstrom bands -- that are partly formed in the upper photosphere and have good sensitivity to acoustic modes. In this article we consider the characteristics of the spatio--temporal Fourier spectra in AIA and HMI observables for a 15-degree region around NOAA Active Region 11072. We map the spatio--temporal-power distribution for the different observables and the HMI Line Core [$I_L$], or Continuum minus Line Depth, and the phase and coherence functions for selected observable pairs, as a function of position and frequency. Five-minute oscillation power in all observables is suppressed in the sunspot and also in plage areas. Above the acoustic cut-off frequency, the behaviour is more complicated: power in HMI $I_C$ is still suppressed in the presence of surface magnetic fields, while power in HMI $I_L$ and the AIA bands is suppressed in areas of surface field but enhanced in an extended area around the active region, and power in HMI $V$ is enhanced in a narrow zone around strong-field concentrations and suppressed in a wider surrounding area. The relative phase of the observables, and their cross-coherence functions, are also altered around the active region. These effects may help us to understand the interaction of waves and magnetic fields in the different layers of the photosphere, and will need to be taken into account in multi-wavelength local helioseismic analysis of active regions.

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