Moss at the LimbThis composite TRACE image shows a layer of moss seen at the Solar limb. The yellow image is a visible light image of the Sun and shows the "solar surface" or photosphere. The blue image is a TRACE 171 Angstrom image showing 1 to 2 million degree coronal loops and a bright "layer" of moss just above the surface. The moss layer is located between about 1500 to 4000 km (1000 - 2500 miles) above the solar surface, much lower than the typical coronal loop apex heights. (Courtesy NASA/GSFC)