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I recently watched a video of someone making an auroral voice contact, and the received audio had a distinctively raspy and disembodied sound to it. Some CW was audible in the background and it had the same sound to it. I understand that this is characteristic of auroral signals.

What mechanism causes this kind of distortion when working via aurora?

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The ionized air associated with aurorae functions as a reflector for radio waves. However, the effective position of the reflection for any given path between two stations moves around rapidly and randomly as a function of the solar wind density and the magnetic field fluctuations. This introduces an extreme amount of phase noise into the signal being reflected. It's like trying to see an image in a mirror that's being shaken around.

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    $\begingroup$ "It's like trying to see an image in a mirror that's being shaken around." now there is an explanation I won't forget, in fact: I will use again and again... thanks Dave! $\endgroup$ – Edwin van Mierlo Jun 17 '16 at 9:19
  • $\begingroup$ Thanks! That's a great explanation. I always pictured the auroral curtain as being flat and moving slowly, but imagining it like a rough and unstable surface makes the sounds I hear make much more sense. $\endgroup$ – Flup Jun 18 '16 at 10:20

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