The EMP, or Electromagnetic pulse, is a rapid magnetic fluctuation which induces pulses of current in unshielded electronics. Natural sources of EMP include lightning, whereas artificial ones include a nuclear
blast.
A nuclear blast generates an EMP via gamma radiation interacting with
air molecules to create Compton electrons. These create a brief current and an associated electromagnetic pulse. This is especially hazardous with an exo-atmospheric nuclear blast
outside the atmosphere, as the region affected by Compton electrons in such a manner becomes enormous and the electrons
will rotate around the
Earth's natural magnetic field lines, creating a vast pulse.
EMPs and NEMPs are extremely hazardous to unshielded electronics, causing rapid fluctuations in current, especially in
long wires or antennae.