MERIDIONAL VARIABILITY FROM LARGE-APERTURE RING DIAGRAMS

摘要

Ring Diagram analysis, a local helioseismology technique, has proven very useful in order to study the solar subsurface velocity flows down to a depth of about O.97R☉ (Hill, 1988). The depth range is determined by the modes used in this type of analysis and thus depends on the size of the area analyzed. Extending the area allows us to detect lower ι modes which penetrate deeper in the Sun. However, there is a compromise between the size of the patch and the validity of the plane wave approximation used by the technique. This paper presents the results of applying ring diagrams to 30° diameter patches over the solar surface in an attempt to reach deeper into the solar interior. Meridional flows are derived using this technique.