DR. ASHOK AMBASTHA

The solar interior is invisible by direct means, and until a few decades back its understanding was based essentially on the surface observations coupled with theoretical models. Advent of helioseismology has provided a “direct” tool to probe the Sun’s internal structure and dynamics by precise detection of solar oscillations trapped in the solar interior. Power of helioseismology has been demonstrated by providing dramatic insight into the properties of solar interior through inversion of frequencies of global acoustic modes, thereby testing the models of solar structure. It has revealed anomalies below the outer convective zone and just outside the solar core. The general agreement between inferred structure of the solar core and solar models strongly indicated that the solution to the solar neutrino problem must result from previously unsuspected properties of the neutrinos, rather than from deficiencies in the solar models. More recent developments in techniques of local helioseismology have begun to provide information about sub-surface weather beneath localized scales of solar active regions; the seats of explosive solar phenomena such as flares and Coronal Mass Ejections (CMEs). These studies have become possible with the availability of high spatial (and temporal) resolution observations of active regions that are improving our understanding of the process of birth and evolution of sunspots and energetic activities observed in the outer layers of solar atmosphere. The success of helioseismology has led to the next obvious step of “Asteroseismology” as applied to distant stars, as oscillating stars are found in most of the HR diagram. In this talk, the speaker shall discuss some of the recent results obtained from the ongoing developments in observational and theoretical techniques.