The study of the Sun has revealed fundamental physical puzzles that have resisted understanding for generations of astronomers. The Sun is a typical star, with other stars being at least as complex. Solving mysteries on the Sun—among others, the dynamo process, the intermittency in the surface magnetoconvection, and the heating of the active corona—is important for all of astronomy and astrophysics. The Sun offers unique opportunities for physical insight that go far beyond just resolving astrophysical processes on their intrinsic scales. These opportunities include (1) using the Sun as a plasma physics laboratory, (2) understanding and predicting the impacts of the Sun on Earth’s climate and on “space weather” in the near-Earth environment, and (3) understanding the role of solar evolution in the evolution of life in planetary systems. The successes achieved in solar research since the 1991 survey report1 lead us to expect that many of these mysteries can be resolved by the new projects prioritized in this report. However, it should be kept in mind that at this time, key solar mechanisms are poorly understood even as they are applied in other astrophysical contexts. Or, fascinating new phenomena might be discovered that will give rise to new puzzles to challenge new generations of physicists.
The progress of the past decade was made possible by investments made in the 1980s that led to revolutionary observational capabilities in space and on the ground, including simultaneous multiwavelength observations of dynamics, precision vector magnetic field measurements, and helioseismology. Breakthroughs in numerical simulations of two-and three-dimensional magnetohydrodynamical (MHD) processes allowed for tailoring solarlike scenarios on the computer. All these advances have led to the formulation of a new strategy—a systems approach—for solar physics in the next decade: