[600MRG] Fantastic conditions NA --> VK, VK --> KH6 : Explanations? Part 3

[James Hollander]

    Third question:  If great circle multihop doesn't explain the remarkable    

    
     
      
       
630m propagation between the USA and Australia the last two nights, then what?  
    Please add your words of wisdom and experience.             
       
     73,  Jim H   W5EST       
       
 OTHER EXPLANATIONS FOR FANTASTIC 630M CONDITIONS 
  1) Skew propagation in a vertical plane delivered the 630m signals mostly along the shortest-distance great circle path from each US TX to each VK RX. That way, some ionospheric slightly-slanting reflective surfaces at far ends in the Pacific path allowed the signal to travel horizontally in the sky and avoid one or more ocean surface reflections.  
   Why could paths originating as far apart as NW USA and SW USA  coincidentally benefit from this convexity?  You only need one slanting surface on XGP path and one surface on the XND path-- both SE of USA in N. Pacific-- to jump start the signals on their way. Closer to Australia only one more slanting surface would bring both signals into their RX destinations. This explanation seems the least demanding of any of the ones I can think of.  But what makes the slanting surfaces?
  2) Duct propagation.  Two surfaces of electron concentration in the ionosphere may have received and supported reflections between the surfaces and carried the signals far with low loss. I find it hard to picture paths originating in NW US and SW US would each or both get a duct that long and wide and lasting for as much as 2-4 hours last night. 

  In Part 4, I'll mention some other ideas that I either don't know enough about or think I should put aside.  Please comment direct to mrsocion at aol.com or post a reply to the reflector as you see fit.