Solar granulation. Computer artwork of granulation on the surface of the Sun. The mottled surface is showing the structure of convection cells in the photosphere (surface) of the Sun. Such a view is obtained by using the Doppler effect to measure motion towards and away from the observer. Dark colours indicate motion toward the observer, light colours show motion away. This motion indicates that convection is occurring, the phenomenon where heated gases and liquids rise, replacing cooler volumes that sink downwards. The continuing effect sets up a circulating convection current.