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Session 29 - Invited Talks.
Invited session, Monday, June 10
Union Theater,

[29.01] First Helioseismic Results from the Global Oscillation Network Group

J. Toomre (JILA, University of Colorado)

Helioseismology studies the internal structure and dynamics of the sun, utilizing very precise measurements of the frequencies of sound waves that propagate throughout the solar interior and are observed at the surface. Efforts to accurately and precisely measure the mode frequencies from a single observing site have met with fundamental limitations imposed by the inevitable interruptions arising from the day-night cycle. To address such problems, the NSF-sponsored Global Oscillation Network Group (GONG) project has developed a network of six identical instruments around the world providing velocity images nearly continuously, a data processing system that can keep up with the massive data flow, and is supported by a vigorous scientific community structured around GONG teams that have shared in all aspects of the development of the project. Though the primary helioseismic data deals with the frequencies and their splittings for the nearly half-million global acoustic modes detectable with the GONG instruments, the data also allows study of how wave fields are locally influenced by flows and magnetic structures below the solar surface, and further provides direct measures of larger-scale flows at the surface.

We shall briefly describe the network, instruments, and data analysis, and then review some of the preliminary scientific results obtained by the teams through inversion of the frequency data, dealing with the structure of the solar interior and the physics of stellar models, and an assessment of the differential rotation profile with depth and latitude. Early results will also be presented concerning nearly steady surface flows of the solar surface.

Program listing for Monday