The outer part of the Sun’s corona, which is illuminated by sunlight scattered or reflected from solid dust particles. The same phenomenon also produces the zodiacal light much farther from the Sun. The dust grains are a few micrometres across, and are located in a disk extending outwards from about 1 solar radius (750 000 km) from the Sun’s surface. Unlike the electrons responsible for the K corona, the dust grains are relatively slow-moving. Thus the light scattered from them has the same spectrum as the photosphere, including its Fraunhofer lines (hence the letter ‘F’). The F corona is the brightest part of the corona beyond 1.5 solar radii from the Sun’s surface.