From: dietz@dls.net   
      
   Gordon D. Pusch wrote:   
      
   >>I suspect EMP will be much, much worse.   
   >   
   >   
   > Almost certainly incorrect, since the gamma-ray energy will be released   
   > over a very long timescale compared to the cyclotron frequency of electrons   
   > in the Earth's magnetic field. Since the gammas are not released as a   
   > sharp pulse, they will not be able to excite coherent electron cyclotron   
   > oscillations in the ionosphere; therefore, EMP effects will in fact be   
   > quite weak compared to a nuclear weapon of comparable yield.   
      
   I don't think the ion cyclotron period is the relevant timescale, Gordon.   
      
   Near the Earth, you get EMP because there's an asymmetry in the   
   current induced by the Compton-scattered electrons.  The magnetic   
   field doesn't come into play at all.   
      
   Above the atmosphere, the EMP is due to the asymmetry in the currents produced   
   by the Earth's magnetic field.  The electrons spiral around the magnetic   
   field lines, but their net motion is north and south.   
      
   	Paul   
      
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