Terms to Know

What Makes the Sun's Appearance Change?

Three reasons:

1. The Sun rotates (see above);
2. The Sun has a strong magnetic field that (probably) gets wound up by the rotation; and
3. There is a tremendous source of energy inside the Sun's interior, and that energy diffuses from the center outwards until it reaches the surface, and then radiates out into the solar system. What could that source of energy be?

The Sun's magnetic field is just like a bar magnet, with a north end and a south end. But it completely flips upside down every 11 years! So really the Sun's activity cycle is 22 years long -- because that's how long it takes to go from north up to south up and back to north up again.

Sunspots are also probably magnetic storms related to the internal magnetic field and the energy flowing out from the Sun's center. They are slightly cooler than the surrounding surface, which makes them look darker.

Lectures

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Astro 100