Spatial Scales and Time Variation of Solar Subsurface Convection

Spectral analysis of the spatial structure solar subphotospheric convection is carried out for subsurface flow maps constructed using time--distance helioseismological technique. The source data are obtained from Helioseismic and Magnetic Imager (HMI) onboard Solar Dynamics Observatory (SDO) 2010 May to 2020 September. A spherical-harmonic transform applied horizontal-velocity-divergence field at depths 0 19~Mm. range scales fairly broad in shallow layers narrows as depth increases. horizontal rapidly increase with depth, supergranulation giant-cell values, indicate existence large-scale convective motions near-surface shear layer. results can naturally be interpreted terms a superposition differently scaled flows localized different intervals. There some tendency toward emergence meridionally elongated (banana-shaped) structures deep layers. total power anticorrelated sunspot-number variation over activity cycle positively correlated larger depths, which suggestive redistribution convective-flow energy due action magnetic fields.