EFFECTS OF THE ATMOSPHERE AND OF SUB-SURFACE FLOWS ON SOLAR OSCILLATION MODES (INVITED REVIEW)

摘要

In helioseismology effects caused by the solar atmosphere on global eigenmodes are gathered in the so-called surface-term. Variations in chromospheric magnetic field, canopy height, temperature or the presence of equilibrium bulk motions all may cause observable frequency shifts of the solar p/f-modes. Surface random or sub-surface global motions (e.g. differential rotation, meridional flow motion) below the solar surface may also have measurable effects on the properties of helioseismic eigenmodes. When both an atmospheric magnetic field and sub-surface flows (i.e. steady state) are present, a complex picture of competition between these two effects is found. The theoretically predicted frequency shifts show promise of explaining some recent GONG, MDI and BiSON observations.