Editing Effects of nuclear explosions (section)

=== Radar blackout===
{{See also|Nuclear blackout|Christofilos effect}}
The heat of the explosion causes air in the vicinity to become ionized, creating the fireball. The free electrons in the fireball affect radio waves, especially at lower frequencies. This causes a large area of the sky to become opaque to radar, especially those operating in the [[VHF]] and [[UHF]] frequencies, which is common for long-range [[early warning radar]]s. The effect is less for higher frequencies in the [[microwave]] region, as well as lasting a shorter time – the effect falls off both in strength and the affected frequencies as the fireball cools and the electrons begin to re-form onto free nuclei.<ref name=bethe>{{cite journal |last1=Garwin |first1=Richard L. |last2=Bethe |first2=Hans A. |title=Anti-Ballistic-Missile Systems |journal=Scientific American |date=1968 |volume=218 |issue=3 |pages=21–31 |doi=10.1038/scientificamerican0368-21 |jstor=24925996 |bibcode=1968SciAm.218c..21G }}</ref>

A second blackout effect is caused by the emission of [[beta particle]]s from the [[fission products]]. These can travel long distances, following the Earth's magnetic field lines. When they reach the upper atmosphere they cause ionization similar to the fireball but over a wider area. Calculations demonstrate that one megaton of fission, typical of a two-megaton H-bomb, will create enough beta radiation to blackout an area {{convert|400|km|miles}} across for five minutes. Careful selection of the burst altitudes and locations can produce an extremely effective radar-blanking effect.<ref name=bethe/> The physical effects giving rise to blackouts also cause EMP, which can also cause power blackouts. The two effects are otherwise unrelated, and the similar naming can be confusing.