9604910 Leibacher Description: This award supports the U.S.-India Cooperative Research: Study of Solar Oscillations Phase III, which will examine the Sun s interior utilizing the data set from the Global Oscillation Network Group (GONG). This recently completed network of six identical oscillation observing stations that circle the globe will keep the Sun under 24 hour surveillance and will yield unique data having importance not only for solar physics, but for astrophysics, solar-terrestrial physics, geophysics, and nuclear physics. The U.S. team is headed by John Leibacher of the National Solar Observatory (NSO), Tucson, and the Indian team by Arvind Bhatnagar, Udaipur Solar Observatory (USO) Udaipur, and S.M. Chitre, Tata Institute of Fundamental Research, Mumbai. The new field of helioseismology has evolved from the discovery of solar acoustic waves that emanate from randomly-excited seismic vibrations from within the Sun. This powerful new tool for studying the Sun s interior structure and dynamics can probe the interior of the Sun with the same precision that terrestrial seismology can probe the Earth s interior. During Phase III of the study, the U.S. and Indian teams will pursue collaborative research in numerous areas that have been stimulated by GONG data. These include inversions; hydrostatic Sun structure; helium abundance in the solar envelope; excitation mechanisms for solar oscillations; background solar spectrum; global magnetic fields in the sun s deep interior; nearly steady flows and magnetic fields; and deterministic detrending. Scope: The U.S.-India component of this large international project is exceptionally well balanced. For the United States, Udaipur has physical attributes such as atmospheric clarity and a unique geographic position on the globe diametrically opposite to Tucson, as well as strong infrastructural resources. Solar physics is a field in which Indian scientists excel. The project will involve USO staff and w orld class researchers from India s premier Tata Institute. For India, the project offers entry to the field of helioseismology, state-of -the-art instrumentation, and involvement in an important international effort. This project has thus far yielded a large number of publications under U.S.-Indian authorship. ***
