This folder contains only content from the glorious MushroomCloud mod, and I honestly couldn't do this myself (although I have made minor edits to make it more usable for this exact case). It is licensed under the MIT license, as found 
https://opensource.org/licenses/MIT
and the original can be found at
https://mods.factorio.com/mod/MushroomCloud
The content of this is was in turn aggregated from:

The animation for the explosion is from
https://mods.factorio.com/mods/Fatmice/UraniumPower
and the high-res is a simple edit made by myself, using my limited abilities to handle editing software.
nuclear-detonation-close-proximity.ogg from https://freesound.org/people/GowlerMusic/sounds/265459/
nuclear-detonation-in-vincinity-1.ogg from https://freesound.org/people/Robinhood76/sounds/270882/
nuclear-explosion-distant-boom-1.ogg from https://freesound.org/people/Innominatus/sounds/231377
nuclear-detonation-in-vincinity-2.ogg from https://www.audioblocks.com/stock-audio/distant-nuke-explosion.html

These are gathered from the Factorio mods page on MushroomCloud, and all the flash effects are from MushroomCloud itself. I do not claim any intelectual property rights over anything in this folder (including the changes I have made).