Editing Nuclear electromagnetic pulse (section)

===Weapon yield===
Typical [[nuclear weapon yield]]s used during [[Cold War]] planning for EMP attacks were in the range of {{convert|1|to|10|MtonTNT|lk=on|abbr=on}}.<ref>{{cite report |title=THREAT POSED BY ELECTROMAGNETIC PULSE (EMP) TO U.S. MILITARY SYSTEMS AND CIVIL INFRASTRUCTURE |author=Committee on National Security {{!}} Military Research and Development Subcommittee |date=1997-07-16 |type=Transcript |docket=H.S.N.C No. 105{{ndash}}18 |publisher=[[United States House of Representatives]] {{!}} [[105th United States Congress]] |location=Washington, D.C. |page=39 |language=en |df=dmy-all |url=https://commdocs.house.gov/committees/security/has197010.000/has197010_1.HTM#39 |access-date=2022-08-11 |url-status=live |archive-url=https://web.archive.org/web/20220811182704/http://commdocs.house.gov/committees/security/has197010.000/has197010_1.HTM |archive-date=2022-08-11}}</ref>{{rp|page=39}} This is roughly 50 to 500 times the size of the Hiroshima and Nagasaki bombs. Physicists have testified at United States Congressional hearings that weapons with yields of {{convert|10|ktonTNT|abbr=on}} or less can produce a large EMP.<ref name="hasc">{{cite report |title=ELECTROMAGNETIC PULSE THREATS TO U.S. MILITARY AND CIVILIAN INFRASTRUCTURE |author=Committee on National Security {{!}} Military Research and Development Subcommittee |date=1999-10-07 |type=Transcript |docket=H.A.S.C. No. 106{{ndash}}31 |publisher=[[United States House of Representatives]] {{!}} [[106th United States Congress]] |location=Washington, D.C. |page=48 |language=en |df=dmy-all |url=https://commdocs.house.gov/committees/security/has280010.000/has280010_0.htm#48 |access-date=2022-08-11 |url-status=live |archive-url=https://web.archive.org/web/20220531152332/http://commdocs.house.gov/committees/security/has280010.000/has280010_0.htm#48 |archive-date=2022-05-31}}</ref>{{rp|page=48}}

The EMP at a fixed distance from an explosion increases at most as the square root of the yield (see the illustration to the right). This means that although a {{convert|10|ktonTNT|abbr=on}} weapon has only {{percentage|7|1000|1}} of the energy release of the {{convert|1.44|MtonTNT|abbr=on}} Starfish Prime test, the EMP will be at least {{percentage|8|100}} as powerful. Since the E1 component of nuclear EMP depends on the prompt gamma-ray output, which was only 0.1% of yield in Starfish Prime but can be {{percentage|5|1000|1}} of yield in low-yield pure [[nuclear fission]] weapons, a {{convert|10|ktonTNT|abbr=on}} bomb can easily be {{math|1=''5'' * ''{{percentage|8|100}}''=''{{percentage|40|100|}}''}} as powerful as the {{convert|1.44|MtonTNT|abbr=on}} Starfish Prime at producing EMP.<ref name="glasstone.blogspot.com"/>{{Unreliable source?|date=December 2022|reason=Blog with annotations (original research?)}}

The total prompt gamma-ray energy in a fission explosion is {{percentage|35|1000|1}} of the yield, but in a {{convert|10|ktonTNT|abbr=on}} detonation the triggering explosive around the bomb core absorbs about {{percentage|85|100|1}} of the prompt gamma rays, so the output is only about {{percentage|5|1000|1}} of the yield. In the [[nuclear fusion|thermonuclear]] Starfish Prime the fission yield was less than 100% and the thicker outer casing absorbed about 95% of the prompt gamma rays from the pusher around the fusion stage. [[Nuclear weapon design#Fusion|Thermonuclear weapons]] are also less efficient at producing EMP because the first stage can pre-ionize the air<ref name="glasstone.blogspot.com"/>{{Unreliable source?|date=December 2022|reason=Blog with annotations (original research?)}} which becomes conductive and hence rapidly shorts out the [[Compton current]]s generated by the [[nuclear fusion|fusion]] stage. Hence, small pure fission weapons with thin cases are far more efficient at causing EMP than most megaton bombs.{{citation needed|date=August 2016}}

This analysis, however, only applies to the fast E1 and E2 components of nuclear EMP. The [[geomagnetic storm]]-like E3 component of nuclear EMP is more closely proportional to the total energy yield of the weapon.<ref name="empcnir">{{cite web |title=Report of the Commission to Assess the Threat to the United States from Electromagnetic Pulse (EMP) Attack. Critical National Infrastructures |author=Electromagnetic Pulse (EMP) Commission |url=https://apps.dtic.mil/sti/pdfs/ADA484672.pdf}}</ref>