Editing Nuclear electromagnetic pulse (section)

===Target distance===
In nuclear EMP all of the components of the electromagnetic pulse are generated outside of the weapon.<ref name="fas"/>

For [[high-altitude nuclear explosion]]s, much of the EMP is generated far from the detonation (where the gamma radiation from the explosion hits the upper atmosphere). This electric field from the EMP is remarkably uniform over the large area affected.{{r|Glasstone_1977}}

According to the standard reference text on nuclear weapons effects published by the U.S. Department of Defense, "The peak electric field (and its amplitude) at the Earth's surface from a high-altitude burst will depend upon the explosion yield, the height of the burst, the location of the observer, and the orientation with respect to the [[geomagnetic field]]. As a general rule, however, the field strength may be expected to be tens of kilovolts per metre over most of the area receiving the EMP radiation."{{r|Glasstone_1977}}

The text also states that, "...{{nbsp}}over most of the area affected by the EMP the electric field strength on the ground would exceed 0.5''E''<sub>max</sub>. For yields of less than a few hundred kilotons, this would not necessarily be true because the field strength at the Earth's tangent could be substantially less than 0.5''E''<sub>max</sub>."{{r|Glasstone_1977}}

(''E''<sub>max</sub> refers to the maximum electric field strength in the affected area.)

In other words, the electric field strength in the entire area that is affected by the EMP will be fairly uniform for weapons with a large gamma-ray output. For smaller weapons, the electric field may fall at a faster rate as distance increases.{{r|Glasstone_1977}}