Taiwan oscillation network: Probing the solar interior

Abstract

In this review paper, we describe the present status of the project of the Taiwan Oscillation Network (TON) and discuss the recent scientific results using the TON data, especially the results from a new method: acoustic imaging. The TON is a ground-based network to measure solar intensity oscillations for the study of the solar interior. Four telescopes have been installed in Tenerife (Spain), Big Bear (USA), Huairou (PRC), and Tashkent (Uzbekistan). The TON telescopes take K-line full-disk solar images of diameter 1000 pixels at a rate of one image per minute. The TON high-spatial-resolution data are specially suitable for the study of local properties of the Sun. Recently we developed a new method, acoustic imaging, to construct the acoustic signals inside the Sun with the acoustic signals measured at the solar surface. From the constructed signals, we can form intensity map and phase-shift map of an active region at various depths. The direct link between the these maps and the subsurface magnetic field suffers from the poor vertical resolution of acoustic imaging. An inversion method is developed to invert the measured phase-shift distribution to estimate the source distribution based on the ray approximation. We also discuss the application of acoustic imaging to image the active regions on the far-side of the Sun that may be used for the solar activity forecast.