Solar physics

Solar physics investigates the Sun’s structure, activity, and physical processes, from its interior and magnetic field to its atmosphere and effects on the Solar System.

Solar dynamo: The process by which motion in electrically conducting solar plasma generates and organizes the Sun’s magnetic field. It explains the magnetic cycle that underlies sunspots and many forms of solar activity.
Sun: The star at the center of the Solar System, a hot sphere of plasma powered by nuclear fusion. Solar physics is the study of this star and its physical processes.
Space weather: Changing conditions in space driven by solar activity and its interaction with planetary environments. Solar eruptions and wind disturbances can disrupt systems throughout near-Earth space.
Sunspot: A relatively dark, cooler region on the solar photosphere associated with concentrated magnetic fields. Sunspot patterns make the changing solar magnetic field visible.
Coronal heating problem: The problem of explaining why the Sun’s corona is far hotter than the photosphere below it. Its resolution must account for how energy reaches and heats the outer atmosphere.
Helioseismology: The study of waves traveling through the Sun to infer its internal structure and dynamics. Oscillations reveal interior conditions that cannot be observed directly.
Plasma: A state of matter containing free charged particles that respond collectively to electromagnetic fields. The Sun is made of plasma, so its behavior differs from that of ordinary gas.
Coronal mass ejection: A large eruption of magnetized plasma from the Sun’s corona into interplanetary space. Tracking these eruptions helps estimate the arrival and strength of geomagnetic disturbances.
Solar cycle: The roughly 11-year cycle in the number of sunspots and other measures of solar magnetic activity. Its recurring pattern is a central test of theories of the solar dynamo.
Solar neutrino problem: The historical discrepancy between predicted and detected solar neutrino flux, resolved through neutrino flavor conversion. It shows how solar observations prompted a major revision in particle physics.

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