A Search for Helioseismic Signature of Emerging Active Regions

Using SOHO/MDI and GONG observations we present time–distance deep-focusing measurements to examine the deeper layers of the solar convective zone. The constructed travel-time maps show 10?–?15 second perturbations at depths of 40?–?75 Mm around active region locations before their emergence to the solar surface. The majority of the active regions used in this study were the same as those used in the recent work published by Ilonidis, Zhao, and Kosovichev (Science 333, 993, 2011). In order to confirm the capability of time–distance measurements to detect emerging active regions, we used a technique similar to their time–distance scheme. Our measurements only in some cases show a similar travel-time anomaly. Additionally, we have shown that the technique utilized in our study can provide more spatial details of the emerging flux configurations.