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Re: (meteorobs) Noctilucent Clouds (fwd)

> Steve H. wrote:  
> I wonder whether there is a connection between
> E-layer radio-reflectivity and the clouds?
> 
> Thomas Ashcraft wrote: 
> I have often wondered about a possible correspondence between noctilucent
> clouds and sporadic-E radio phenomena. Does anyone know if radio meteor
> observers, sporadic-E monitors ( known as radio DX'ers ), and NLC observers
> have ever compared data? 
> 
> I wonder if there is a periodic comet related meteor dust quality that is
> under the threshold of incandescence so that a meteoric particle would
> neither be visually detectable nor reflective of individual radio scatter
> bursts. 
> 
> I wonder if there are certain cometary meteor showers ( as yet to be
> discovered? ) that are made up of particles so fine that they are not
> detectable as "normal" meteor showers but in fact cause a distinct infusion
> of dust into the ionosphere resulting in sporadic-E and NLC. 
> 
> Has this topic been studied well?

I forwarded the discussion to our local radio-propagation expert and
occasional meteor observer Geoff Grayer.  This is his reply:

   Yes, this suggestion has been made many times. I myself looked into
   this; the heights of both are accurately known, and the nc's occur
   significantly lower than the Es layers; time of observation is
   different; and as far as I know, there has been no correlation
   between days when nc's have been observed and extreme excursions of
   Es happened.

   Incidentally, Es occurs on the HF and lower VHF bands very
   frequently in the summer months; its excursions producing a
   critical frequency above 100 MHz are however much rarer in this
   part of the world.

   For further information on Es and its theories, including my views
   on its connection with meteors, all based on scientific
   observations and some of my own work,I suggest you read "The
   VHF/UHF DX Book", ed. I. F. White, ISBN 0 9520468 0 6, Chapter 2
   "VHF/UHF Propagation" by Dr G.H. Grayer G3NAQ/AE4PI; published for
   the Radio Society of Great Britain and also obtainable from the
   American Radio Relay League.


Malcolm
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