Electromagnetic pulse

Electromagnetic Pulse, or EMP is the electromagnetic radiation from an explosion (especially a nuclear explosion) or an intensely fluctuating magnetic field caused by Compton-recoil electrons and photoelectrons from photons scattered in the materials of the electronic or explosive device or in a surrounding medium. The resulting electric and magnetic fields may couple with electrical/electronic systems to produce damaging current and voltage surges. The effects are usually not noticeable beyond the blast radius unless the device is nuclear or specifically designed to produce an electromagnetic shockwave. An alternate definition is: a broadband, high-intensity, short-duration burst of electromagnetic energy.

The worst of an electromagnetic pulse generally only lasts for a second, but any unprotected electrical equipment will be affected by the pulse.

EMP is mentioned several times in the Halo Universe:
 * The Power Drain uses EMP to disable shields, vehicles and other power sources.
 * The Vampire's Stasis Drain Cannon uses EMP as well to drain power from enemy aircraft.
 * Professor Anders' vehicle, the Gremlin, uses EMP as main armament to disable enemy non-infantry units.
 * A charged Plasma Pistol blast will temporarily disable vehicles and energy shields much like the power drain.
 * The Deep-Space Artifact let out an enormous electromagnetic pulse that briefly canceled out all communications in the Sol System. It later let out another pulse upon deactivation.
 * The detonation of Shiva-class Nuclear Warheads are almost always followed by a massive electromagnetic pulse.
 * In Halo: First Strike, John-117 used a Plasma Grenade's EMP charge to disable the electronics of a locked door on Ascendant Justice. This allowed him to open the door.
 * The in-atmosphere jumping of the Prophet of Regret's Assault Carrier to Slipspace above New Mombasa creates a massive purple electromagnetic pulse that devastated the city, and fried the navigational and safety systems of nearly five dozen SOEIV pods unfortunate enough to drop into the city at that exact moment, plunging them and the Orbital Drop Shock Troopers inside free-falling to certain death.
 * In Two Betrayals, Cortana diverts John's energy shields into an EMP to disable Halo's pulse generators.

Trivia

 * If you disable a vehicle using an EMP, it will show an animation of some sparks flying around but if you disable it again before it is drivable then the animation will stop and the vehicle will not work.
 * A vehicle disabled by an EMP will still have full functionality of its weapons if it has any. For example, if a Warthog is disabled by an EMP, the turret will still be able to turn around and shoot, making practical use of the EMP tricky.