太阳近表面剪切层中与磁活动的关联 I. 自转
Correlations with Magnetic Activity in the Solar Near-Surface Shear Layer. I. Rotation
浏览论文内容
中文总结 AI 辅助
该研究利用Helioseismic and Magnetic Imager数据和环图分析，发现太阳近表面剪切层自转与磁活动存在显著纬度相关的多年滞后关联，且存在半球差异，为研究太阳周期演化提供了新依据。
中文摘要 AI 辅助
我们利用日震与磁成像仪（Helioseismic and Magnetic Imager）的数据确定了近表面剪切层的自转速率及其时间变化。我们应用环图分析技术，该技术可探测深度在1 Mm至17 Mm之间的层区。我们发现自转速率随深度增加而增大；在较深层，其值与全球日震分析推断的结果一致，但南北半球的自转速率存在差异。我们表明，即使不减去每个历元的时间平均自转速率，也能确定自转速率的时间变化；不过，要得到典型的“扭转振荡”信号，则需要进行此类减法。我们发现，即使在浅至1 Mm的深度，自转也呈现出典型的扭转振荡模式。由残余流推断的累积纬向位移表现出明显的高纬度半球不对称性，并在太阳周期时间尺度上变化；在75°纬度处，其与极区磁场存在明显的时间关联。我们发现，在部分纬度上，累积位移与磁活动存在显著相关性，且存在多年滞后：在15°附近，位移领先磁活动约5年；而在更高纬度，磁活动领先约4年。在中高纬度，推断的滞后呈现半球依赖性，磁活动倾向于在北半球领先、在南半球滞后，这表明太阳周期演化的时间可能存在半球差异，需要更长的时间序列来检验周期间的变化。
英文摘要
We used data from the Helioseismic and Magnetic Imager to determine the rotation rate of the near-surface shear layer and its time variation. We applied the ring-diagram analysis technique allowing us to probe the layer between the depths of 1 Mm and 17 Mm. We find that the rotation rate increases inwards; it reaches values consistent with those inferred from global helioseismic analyses in the deeper layers, however, there are differences in the rotation rate of the northern and southern hemispheres. We show that the time variation of the rotation rate can be determined even without subtracting the time-averaged rotation rate from each epoch; however, such a subtraction is needed to get the canonical ``torsional oscillation'' signal. We find that even at depths as shallow as 1 Mm, the rotation rate shows the typical torsional oscillation pattern. The cumulative zonal displacement inferred from the residual flows exhibits a pronounced high-latitude hemispheric asymmetry and varies on solar-cycle timescales; at $75^\circ$ it shows an apparent temporal association with the polar magnetic field. We find significant correlations between the cumulative displacement and magnetic activity at a subset of latitudes, with multi-year lags: the displacement leads activity by ~5 years near $15^\circ$, whereas at higher latitudes activity leads by ~4 years. At mid to high latitudes, the inferred lags show a hemispheric dependence, with activity tending to lead in the north and lag in the south, suggesting possible hemispheric differences in the timing of cycle evolution and motivating longer time series to test cycle-to-cycle variation.
