Accompanying the article "Magnetars," by Kouveliotou, et al, Scientific American, February, 2003, is a graphic labeled "Extreme Magnetism" which shows four ways in which "Magnetar fields wreak havoc with radiation and matter." One of these ways is spontaneous (my word) Photon Splitting, described as "In a related effect, x-rays freely split in two or merge together. This process is important in fields stronger than 10^14 gauss." I have trouble visualizing or understanding this process by which a photon can split or merge with another photon which doesn't involve some other particle (e.g., an electron). If someone could elaborate in layman terms, it would be appreciated. FWIW, the three other ways listed are Vacuum Birefringence, Scattering Suppression, and Distortion of Atoms.