Spatial Spectrum of Solar Convection from Helioseismic Data: Flow Scales and Time Variations

TL;DR

This study investigates the spectral properties of solar convection at various depths using helioseismic data, revealing how flow scales and power vary with depth and solar activity cycle.

Contribution

It provides new insights into the depth-dependent flow scales and their variation with the solar activity cycle based on extensive helioseismic observations.

Findings

Flow scales increase with depth from supergranulation to giant cells.

Convective flow power correlates with the solar activity cycle.

Surface and deep flow behaviors show opposite trends during solar maximum.

Abstract

We analyze spectral properties of solar convection in the range of depths from 0 to 19~Mm using subsurface flow maps obtained by the time-distance heiioseismology analysis of solar-oscillation data from the Helioseismic and Magnetic Imager (HMI) onboard Solar Dynamics Observatory (SDO) from May 2010 to September 2020. The results reveal a rapid increase of the horizontal flow scales with the depth, from supergranulation to giant-cell scales, and support the evidence of large-scale convection, previously detected by tracking the motion of supergranular cells on the surface. The total power of convective flows correlates with the solar activity cycle. During the solar maximum, the total power decreases in shallow subsurface layers and increases in the deeper layers.