Study of Chromospheric Global-Scale Flows using Local Correlation Tracking Across the past 10 Solar Cycles
Abstract
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.
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BibTeX
@misc{li2026study,
title = {{Study of Chromospheric Global-Scale Flows using Local Correlation Tracking Across the past 10 Solar Cycles}},
author = {Qin Li and Yan Xu and Keiji Hayashi and Chunlei Liang and Haimin Wang},
howpublished = {arXiv},
year = {2026},
month = sep,
doi = {10.48550/arxiv.2609.28890},
eprint = {2609.28890},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2609.28890},
note = {CC BY 4.0},
}
RIS
TY - UNPB
TI - Study of Chromospheric Global-Scale Flows using Local Correlation Tracking Across the past 10 Solar Cycles
AU - Qin Li
AU - Yan Xu
AU - Keiji Hayashi
AU - Chunlei Liang
AU - Haimin Wang
PY - 2026
DA - 2026/09/24
PB - arXiv
DO - 10.48550/arxiv.2609.28890
UR - https://arxiv.org/abs/2609.28890
AB - 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.
ER -