Quasi-biennial variations in helioseismic frequencies: can the source of the variation be localized?
Quasi-biennial variations in helioseismic frequencies: can the source of the variation be localized?
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日震频率的准两年变化：变化来源能否定位？
DOI：
10.1111/j.1365-2966.2011.20123.x
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发表时间：
2011
影响因子：
4.8
通讯作者：
R. Simoniello
中科院分区：
文献类型：
--
作者：
A. Broomhall;W. Chaplin;Y. Elsworth;R. Simoniello
我们调查的球谐度（l）的依赖性的“地震”准两年振荡（QBO）观察到的低阶太阳p模式的频率，使用太阳作为一个明星伯明翰太阳振荡网络数据。地震QBO的振幅调制的11年的太阳活动周期，在太阳极大的信号的振幅最大。对于l = 2和3模式，信号的幅度明显大于l = 0和1模式。地震QBO表现出一定的频率依赖性，但这种依赖性是不那么强，在11年的太阳周期观察。这些结果与地震QBO起源于内部浅层（一种可能性是剪切层底部延伸到太阳表面以下5%）是一致的。在这种情况下，负责地震QBO的磁通量被带到表面（其对p模式的影响更强）的浮力通量从11年的周期，其中的强成分主要是在低纬度地区观察。由于l = 2和3模比l = 0和1模对赤道纬度更为敏感，11年周期对地震QBO的影响在l = 2和3模频率上更为明显。我们的研究结果表明，接近太阳极大期的地震QBO的主要影响发生在低纬度地区（<45 ° C），这是11年太阳周期的强成分驻留。要隔离纬度的依赖性地震QBO从11年的太阳周期，我们必须考虑的时代时，11年的太阳周期是弱的。然而，远离太阳活动极大期，地震QBO的振幅很弱，使得纬度依赖性难以抑制。
We investigate the spherical harmonic degree (l) dependence of the ‘seismic’ quasi-biennial oscillation (QBO) observed in low-degree solar p-mode frequencies, using Sun-as-a-star Birmingham Solar Oscillations Network data. The amplitude of the seismic QBO is modulated by the 11-yr solar cycle, with the amplitude of the signal being largest at solar maximum. The amplitude of the signal is noticeably larger for the l = 2 and 3 modes than for the l = 0 and 1 modes. The seismic QBO shows some frequency dependence but this dependence is not as strong as observed in the 11-yr solar cycle. These results are consistent with the seismic QBO having its origins in shallow layers of the interior (one possibility being the bottom of the shear layer extending 5 per cent below the solar surface). Under this scenario the magnetic flux responsible for the seismic QBO is brought to the surface (where its influence on the p modes is stronger) by buoyant flux from the 11-yr cycle, the strong component of which is observed at predominantly low latitudes. As the l = 2 and 3 modes are much more sensitive to equatorial latitudes than the l = 0 and 1 modes the influence of the 11-yr cycle on the seismic QBO is more visible in l = 2 and 3 mode frequencies. Our results imply that close to solar maximum the main influence of the seismic QBO occurs at low latitudes ( <45 ◦ ), which is where the strong component of the 11-yr solar cycle resides. To isolate the latitudinal dependence of the seismic QBO from the 11-yr solar cycle we must consider epochs when the 11-yr solar cycle is weak. However, away from solar maximum, the amplitude of the seismic QBO is weak making the latitudinal dependence hard to constrain.