I meant EMPing the ground from orbit. I'm not convinced that radionucleotide chaff will do anything persistent in orbit; bombs have been detonated there before (hence why we know about HAEMP), the extra radiation belts don't last long.

in that case, the effect was hypothesized, later observed and understood. a deliberated RF denial involving munitions salted for the purpose is quite do-able. w/o specifics, an enduring denial munition may be engineered, however the perp would also have to endure the effect, as well as any response from the rest of the planet.