Photon energies in particle production. Similar to Fig. 1, but showing photon ﹩\epsilon _{\perp }﹩ (energy in a frame where ﹩\boldsymbol{k}{\boldsymbol{\cdot}} \boldsymbol{B}=0﹩) vs. altitude. The energy shown is that of the parent photon for the pair production events and of the emitted photon for the synchrotron events. Note that many synchrotron photons are often emitted right at the sites of pair creation seen in Fig. 1. It is evident that many of these secondary photons are born with insufficient ﹩\epsilon _{\perp }﹩ (<2) to create another pair, unless their angle with ﹩\boldsymbol{B}﹩ increases significantly.