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arXiv · 2206.10751

Contribution of flows around active regions to the north-south helioseismic travel-time measurements

Paul-Louis Poulier·Zhi-Chao Liang·Damien Fournier·Laurent Gizon
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Abstract

Context. In local helioseismology, the travel times of acoustic waves propagating in opposite directions along the same meridian inform us about horizontal flows in the north-south direction. The longitudinal averages of the north-south helioseismic travel-time shifts vary with the sunspot cycle. Aims. We aim to study the contribution of inflows into solar active regions to this solar-cycle variation. Methods. To do so, we identify the local flows around active regions in the horizontal flow maps obtained from correlation tracking of granulation in SDO/HMI continuum images. We compute the forward-modeled travel-time perturbations caused by these inflows using 3D sensitivity kernels. In order to compare with the observations, we average these forward-modeled travel-time perturbations over longitude and time in the same way as the measured travel times. Results. The forward-modeling approach shows that the inflows associated with active regions may account for only a fraction of the solar-cycle variations in the north-south travel-time measurements. Conclusions. The travel-time perturbations caused by the large-scale inflows surrounding the active regions do not explain in full the solar-cycle variations seen in the helioseismic measurements of the meridional circulation. Keywords: Sun: activity -- Sun: helioseismology

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Paul-Louis Poulier, Zhi-Chao Liang, Damien Fournier, Laurent Gizon. 2022-06-21. Contribution of flows around active regions to the north-south helioseismic travel-time measurements. https://doi.org/10.1051/0004-6361%2F202243476

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