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arXiv · 2508.12465

Activity-Cycle Variations of Convection Scales in Subsurface Layers of the Sun

Alexander V. Getling·Alexander G. Kosovichev
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Abstract

We use subsurface-flow velocity maps inferred by time--distance helioseismology from Doppler measurements with the Helioseismic and Magnetic Imager (HMI) of the Solar Dynamics Observatory (SDO) to investigate variations of large-scale convection during Solar Cycles 24 and 25 in the 19-Mm-deep layer. The spatial power spectra of the horizontal-flow divergence reveal well-defined characteristic scales of solar supergranulation in the upper 4 Mm layer, while the giant-cell scale is prominent below levels of d ~ 8 Mm. We find that the characteristic scales of supergranulation remain stable while the giant scales increase during the periods of the 11-year activity cycle maxima. The power of the giant-cell scales increases with the enhancement of solar activity. This may be due to large-scale flows around active regions and, presumably, solar-cycle variations of the convection-zone stratification.

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Alexander V. Getling, Alexander G. Kosovichev. 2025-08-17. Activity-Cycle Variations of Convection Scales in Subsurface Layers of the Sun. https://doi.org/10.1007/s11207-025-02546-5

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