发表机构
Institute for Space Weather Sciences, New Jersey Institute of Technology; Department of Mechanical and Aerospace Engineering, Clarkson University（太空天气科学研究所，新泽西理工学院; 机械与航空航天工程系，克拉克森大学）
机构由 AI 辅助整理，请以论文原文为准。AI 中文总结
利用科代卡纳尔观测站1907-2007年Ca II K数据的LCT技术，研究了太阳活动周14-23的较差自转和经向流动，发现较差自转变化小，经向流动极向且周际变化大，并与SDO/HMI数据高度相关。
AI 中文摘要
全球尺度的太阳表面流动，包括较差自转和经向环流，为太阳发电机提供了关键的观测约束。我们利用本地相关跟踪（LCT）技术，对来自科代卡纳尔太阳观测站的数字化Ca II K观测中的色球强度结构进行了研究，这些观测覆盖了太阳活动周（SC）14至23（1907年至2007年）。最有价值的数据覆盖来自活动周14至19，原因有二：（1）它提供了早期活动周的记录，这些记录通常不易获得；（2）其占空比远优于活动周20至23的数据，因此测量误差要小得多。另一方面，活动周20至23的信息损失由其他现代空间观测所弥补。恢复的较差自转显示出相对较小的周际变化，并保持接近Howard参考轮廓。在采样良好的SC 15至19期间，低纬度和中纬度出现的重复纬向流动残余带与活动带大致相关。经向流动在早期记录中主要朝向极区，并表现出较大的相对周际变化和不确定性。SC 14的不完整覆盖以及SC 21至23期间的稀疏采样限制了对覆盖较好的SC 15至20的详细比较。与其直接后继者SC 19（记录中最强的活动周）相比，SC 18表现出更强且连续的北向极向经向分支，其峰值出现在太阳黑子极大期前两到三年。SC 19则显示出在其自身极大期之前较早达到的较小增强。使用PSPT观测进行的独立比较得出，LCT与SDO/HMI经向流动剖面之间的全周期相关系数为r=0.91。这些结果将太阳活动周相关流动的观测背景扩展到了一个多世纪，并推动了通过数据驱动重建进行进一步改进。
英文摘要
Global-scale solar surface flows, including differential rotation and meridional circulation, provide key observational constraints on the solar dynamo. We investigate these flows using local correlation tracking (LCT) of chromospheric intensity structures in digitized \ion{Ca}{2}~K observations from the Kodaikanal Solar Observatory covering Solar Cycles (SC) 14 to 23 (1907 -- 2007). The most valuable data coverage are from cycles 14 to 19 for two reasons: (1) it provided record for early cycles that are not commonly available; (2) it had much better duty cycle than the data of cycles 20-23, therefore the measurements had much less errors. On the other hand, the information loss in cycles 20-23 are compensated by other modern space observations. The recovered differential rotation shows relatively small cycle-to-cycle variations and remains close to the Howard reference profile. Recurring zonal-flow residual bands at low and middle latitudes are broadly associated with the activity belts during the well-sampled SC~15--19. The meridional flow is predominantly poleward in the earlier record and exhibits larger relative cycle-to-cycle variations and uncertainties. Incomplete coverage of SC~14 and sparse sampling during SC~21--23 limit detailed comparisons to the better-covered SC~15--20. Compared with its immediate successor SC~19, the strongest cycle in the record, SC~18 exhibits a stronger and continuous northern poleward meridional branch, peaking two to three years before its sunspot maximum. SC~19 shows a minor enhancement that peaks earlier prior to its own maximum. An independent comparison using PSPT observations yields a full-period correlation of $r=0.91$ between the LCT and SDO/HMI meridional-flow profiles. These results extend the observational context for solar-cycle-related flows over a century and motivate further refinement through data-driven reconstruction.
