Regarding your other comment: why wouldn't a high-altitude detonation, even outside the atmosphere cause an EMP? I feel like the gamma photons emitted in space will eventually hit the atmosphere and with that cause electrons to spiral along field lines. Isn't the question just one of intensity?
Or is it largely dependent on multi-photon interactions to impart enough impulse on the electrons?
Or is it largely dependent on multi-photon interactions to impart enough impulse on the electrons?