solar magnetic fields, and the surface pressure waves (p-modes). Further, ground-based observations provide the critical data required by the designers of space missions. Finally, ongoing nighttime observations of brightness and magnetic activity of distant solar-type stars are demonstrating the varying states of activity the Sun may have achieved in other centuries. These observations, combined with data on Earth's atmosphere, indicate that variations in the Sun's radiative and plasma emissions are capable of influencing the weather and climate at Earth's surface.
The task group believes that the primary tasks of ground-based telescopic research should be the following:
Obtaining a long-term synoptic record of solar activity: The National Solar Observatory, the High Altitude Observatory (HAO), and independent observatories—including, for example, Mt. Wilson, Stanford-Wilcox, Big Bear, San Fernando, and Marshall Space Flight Center—have an important role in this effort.
Studying the solar interior and the generation of magnetic fields by mapping subsurface flows and interior magnetic fields through long-term helioseismological observations; and
Observing the interaction of convection, magnetic fields, and radiative transfer by imaging with high spatial, temporal, and spectral resolution.
For convenience, the task group divided its discussion of the current U.S. ground-based solar research program into (1) major solar observational facilities; (2) data, theory, and modeling; and (3) people, programs, and institutions—the means by which elements 1 and 2 are integrated to advance scientific understanding.
The National Solar Observatory, a multisite facility of the National Optical Astronomy Observatories (NOAO), is operated by the Association of Universities for Research in Astronomy (AURA) under a cooperative agreement with the National Science Foundation. The current responsibilities of the NSO include the following:
Continued operation of the Kitt Peak (NSO/KP), Sacramento Peak (NSO/SP, “Sac Peak”), and Tucson facilities;
Operation and upgrade of the multisited telescopes of the Global Oscillations Network Group (GONG) for continuous studies in helioseismology;
Fabrication and operation of the SOLIS array for synoptic optical long-term investigation of the Sun; and
Archiving and distribution of data, and providing specialist-supported access to NSO observing facilities.
The NSO operates the two largest U.S. telescopes for ground-based solar observation—the McMath-Pierce telescope at Kitt Peak (commissioned in 1961) and the Vacuum Tower Telescope (VTT) at Sac Peak (commissioned in 1969). NSO facilities are available to both local staff and visiting scientists worldwide. To maximize scientific productivity, NSO policy