Granules on the sun are small, round features that appear on the surface of the sun. They are caused by convection, which is the movement of hot plasma within the sun's interior.
Granules are part of both the photosphere and the convection zone. The photosphere is the visible surface of the sun, and the convection zone is the layer just below it where convection takes place. Granules form at the top of the convection zone and are visible on the photosphere.
Granules form when hot plasma rises from the interior of the sun, cools at the surface, and sinks back down. This process is known as convection. As the plasma sinks, it creates a depression on the photosphere, which is surrounded by brighter, hotter plasma. This creates the appearance of granules.
The average size of a granule on the sun is about 1,500 kilometers in diameter. However, they can range in size from 1,000 to 2,500 kilometers.
Granules do not directly impact solar activity, but they are closely related to sunspots, which do have an effect. Sunspots are areas where the magnetic field is concentrated, and they often form around the edges of granules. This can lead to solar flares and other solar activity.