Don't know if this is anything like what you're trying to achieve. I turned off sun, atmosphere etc. to let you see more clearly what's happening. The spiral on the left has just the lava material applied, and I cranked up the ambience and diffusion a lot. Also, I put the bead for diffusion in the A channel The right-hand one, I duplicated the spiral, moved it to the right, then duplicated it again and changed the duplicate to a radial light.