Title: Identification of Far Side Events.
Authors: Irene Gonzalez Hernandez and the GONG and MDI far-side teams.
Synoptic maps of the non-visible disk (far side) of the Sun calculated using seismic holography have proved to be very reliable for detecting large active regions before they rotate onto the visible hemisphere. Time-distance analysis has shown similar capability to map the far-side magnetic activity. Calibrating the far-side signatures in terms of physical parameters such as active-region size and magnetic field strength is crucial in the Space Weather context. A significant correlation between far-side signature and the total area of the active region is found when comparing helioseismic maps of large active regions on the far side of the Sun with magnetic images of the same active regions on the the visible hemisphere before and after their passage across the far hemisphere. Using the same type of analysis, an approximately logarithmic increase in the seismic phase shift with increasing magnetic field strengths above a critical field of ~20 Gauss is found. Recently the far-side technique has been extended to cover up to 30-degrees into the front-side of the Sun. This new development allows the direct comparison of the seismic signatures with the superficial magnetic structure, which will help improve the calibration in terms of physical observables. Preliminary work combining MDI and GONG far-side maps encourages further research in this direction. The combination of data from both instruments could lead to an improvement in the prediction capability of the technique, as well as to a better understanding of the spurious, non persistent seismic signal associated with the far-side images and better discrimination between solar and instrumental noise in anticipation of HMI data.