Energy Source
Nuclear fusion hydrogen burning
How can the protons get together?
Needs 15 million K and 100+ g/cm3 gravitational equilibrium
Interior
How do we know?
Neutrinos 1 2 and vibrations and physics
How does the energy get out? Slowly.
Atmosphere
Why sunspots? Magnetic fields Zeeman effect
Coronal loops Eruptions Flares x-ray flare multi-wavelength
Sunspot cycle
Effects on the Earth