I love granulation, there are some amazing videos of it and it reminds me of billions of worms or maggots all crawling over each other 🙂
Granules on the “photosphere” of the Sun are caused by convection currents of plasma within the Sun’s “convective” zone. The grainy look is produced by the tops of these convective cells and is called granulation.
I don’t think anyone knows exactly what is going on with granulation, but I don’t think it is directly due to the magnetic field changing like that. The magnetic field at the Sun does change, but not that quickly. However, plasma can get ‘stuck’ to magnetic field, so if the plasma moves around that fast maybe it could take the mag field with it…..
The rising part of the granules is located in the center where the plasma is hotter. The outer edge of the granules is darker due to the cooler descending plasma. In addition to the visible appearance, Doppler shift measurements of the light from individual granules provides evidence for the convective nature of the granules.