Re: Does EMP work the same way in and out of the atmosphere?

Dear David:

I cannot find a specific reference to an answer to your question, but from 
my experience working in the atomic-weapons program I would answer your 
question as follows:

The Electromagnetic Pulse from the atomic explosion is created by the rapid 
expansion of the fireball from the explosion.   This pulse may be somewhat 
effected by the presence of the atmosphere, but the EMP is created even in 
the vacuum of outer space since it is primarily derived from the expansion 
of the materials in the weapon.  The negative electrons move at very high 
velocities compared to the heavy positive ions created in the explosion, 
the result being that a very large electromagnetic pulse is generated by 
the separation of the very large amount of positive and negative charges.  
That is why atomic weapons in space would will be very effective in 
dstroying integrated circuits.   

There may well be some difference in the atmosphere because the electrons 
are slowed down in the atmosphere as compared in outer space,  and most 
probably the pulse in outer space would be greater.   So depending upon how 
your story goes you could say that the vacuum would work in the atmosphere 
but not in outer space; or you could say that the vacuum tube would work in 
both places.  Depending upon the vacuum tube design either situation could 
be true.  So I think you can feel free to write the story whichever way you 
think makes a better story!  Remember is is fiction anyhow!

However in actual fact the pulse would be bigger in outer space.


Richard Bersin.......

Admin note:

My apologies, it has been a while since I considered these kind of issues, and 
I tend to avoid them.  But you should know that the electromagnetic pulse of 
most concern is due to the interaction of nuclear device generated gamma 
radiation with the atmosphere.  Therefore, EMP effects are of little or no 
concern for a nuclear device detonated in space unless, of course, you are 
concerned with nuclear devices detonated so close to a target that gamma 
radiation interactions with atoms of the target give rise to what is referred 
to as an EMP source region.  But then, if you are that close, the target will 
probably experience effects far more significant than those due to 
electromagnetic phenomena generated interior to the target.

Your further research of this topic may be somewhat difficult.  (:  i.e., it's 
not the kind of information that is readily distributed.  Your best bet would 
be to spend some considerable time searching through the archived government 
publications at larger university libraries.

Sidney Chivers, nuclear engineering - retired