In a word, no. There is no risk of an "accidental detonation" caused by a magnetic storm, and there wouldn't be one even if you put the warhead upstream the bow shock directly in the path of the CME.
On the other hand, if a LEO satellite's electronics get fried, sooner or later it will burn up in the atmosphere since it cannot maneuver anymore, and if it carries a load of weapons-grade uranium it's going to be a somewhat unpleasant event, as you imagine.
On the other hand, if a LEO satellite's electronics get fried, sooner or later it will burn up in the atmosphere since it cannot maneuver anymore, and if it carries a load of weapons-grade uranium it's going to be a somewhat unpleasant event, as you imagine.