The visible surface of the Sun is a layer called the photosphere. This layer is a thin shell of hot, ionised gases or plasma about 400 km thick. Most of the energy radiated by the Sun passes through this layer. From Earth, the surface looks smooth, but it is actually turbulent and granular because of convection currents.
Solar Cycle Sunspot Number Sunspot Group Sunspot Cycle Michelson Doppler Imager
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