2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/85696This note considers two related topics regarding the {\it self-induced charge current} in the experiments detecting photon rest mass: (i) the effective rest mass, $(0.3\sim 1)\times 10^{-54}$ Kg, of photons arising from the ions in the secondary cosmic ray is compared to Luo {\it et al.}'s new upper limit on photon rest mass ($1.2\times 10^{-54}$ Kg); (ii) there are two main classes of experiments to detect photon rest mass based respectively on the Ampère-Maxwell-Proca equation and the Lagrangian (or Hamiltonian) density of electromagnetically interacting system.3 pages, LatexClassical PhysicsGeneral Physicstext