Manipura. The third center of force is commonly known as the "navel lotus" because it is situated in the lumbar region, opposite the navel. It appears to clairvoyant vision as "the color of heavy-laden rain clouds." Ten nadis emanate from this center, which is related to fire.
Ralph Adamson has captured the movement of kundalini energy on its assent through the body, illuminating the third chakra as a path is made to the heart chakra. Notice the brow chakra is already beginning to glow.