Photon-photon collisions are still technically possible... I remember a professor mentioning this as one question he got in grad school... draw out the Feynman

Photon-photon collisions are still technically possible... I remember a professor mentioning this as one question he got in grad school... draw out the Feynman diagram and you see a vanishingly small probability of photon-photon interaction. But yeah. Ionized particles like Galactic Cosmic Rays can be repelled by the local stellar magnetic field, but mostly the lower energy rays are deflected. Higher energy -to-charge-ratio GCRs can punch right through the weak stellar magnetic field, just like do for our Sun’s interplanetary magnetic field.