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(meteorobs) Question on radio meteors - Sporadic E ?

Date: Tue, 11 May 1999 16:19:46 +0100
From: Malcolm <malcolmp@ukonline.codot uk>
Subject: Re: (meteorobs) Question on radio meteors - Sporadic E ?

Michael Boschat <andromed@atm.daldot ca> said :
> I monitor 83.25 MHz but from the 4th have had awful reception and no
>meteors heard. 
snip
>if there is a simple way to know
>if any Sproadic-E is present?
- ----

********************************************************************* 
Let me clarify (even disagree!) with a few points in the following
(otherwise excellent) summary of sporadic-E etc...
Geoff Grayer (G3NAQ/AE4PI), member of the RSGB Propagation Studies
Committee, and author of "VHF/UHF Propagation", Chapter 2
of The VHF/UHF DX Book (ed. Ian White, G3SEK), ISBN 0 9520468 0 6
*********************************************************************

Malcolm (callsign?) writes:

( Caveat : Here in Europe ,,, )

The simplest way is by ear!
Sporadic-E is a localised area of enhanced 'reflectivity'.
Thus it favours stations in one direction but not another.
The localising effect is more pronounced the higher the frequency.
Thus, for example, here in the UK we may hear stations in NW Italy
on 144MHz but from a large area in SE France, Switzerland, and Northern
Italy on 50MHz, during an event.
It is very sporadic ( would you believe ! :-)  ) in that a station may
be 5&9++ one moment and gone altogether a few seconds later. Other
times it may persist for minutes or hours. Longer at low frequencies
than at the higher end. Sporadic in direction also. An event giving
propagation to Sardinia may fade out to be replaced by one to Spain.
It is mainly a daylight phenomenon, again particularily at the higher
freq.
Malcolm.

*********************************************************************
There is a characteristic double peaked diurnal distribution, which
becomes more distinct as the frequency increases, he maxima occurring
at around 1200 and 1800 hrs local time.                Geoff.
*********************************************************************

The progression of a Sporadic-E enhancement can be monitored on a
panoramic receiver, watching the spectrum fill up from 25MHz on up
through 50MHz then into 100MHz etc. as the event intensifies.
However that really only works at low solar cycle.
At this time in the solar cycle the picture is confused by regular
E and F-layer propagation in the high HF and low VHF.
Malcolm.

***********************************************************************
"Regular" E layer propagation DOES NOT DEPEND ON THE SOLAR CYCLE (unlike
the higher F-layer, which is highly dependant). Ths can easly be illustrated
by plotting the maximim daily F layer critical frequency throughout the year
over a solar cycle; they all look the same. Why is this? Well the F
layer is produced by the more energetic and therefore more interactive 
radiations and particles, which are only emitted from active areas on the
sun. By the time you get down to the lower E-layer, it is the "softer"
radiation, the ultra-violet which produces the ionisation. This of course
is just beyond the visible range. And you know from observation that the
output of the sun in the visible does not noticably vary during an 11-year
cycle! (In fact there is about a 1% decrease at solar maximum, due to the
area of the sun covered by dark sunspots).

The question of whether Es varies during the solar cycle is still problematic.
There is some suggestion that it DECREASES during solar maximum (possibly
because increased magnetic disturbances prevent the Es layers forming). My own
correlation analysis of 144 MHz Es data over one solar cycle (so far
unpublished)
suggests this indeed to be the case, but the data is insufficient for the
results
to be statistically convincing.                                   Geoff.
***************************************************************************

I am not sure about F-layer, but could regular E-layer extend up to
80MHz at this time ? Not sure. Could this be the cause perhaps ?
Malcolm.

**********************************************************************
F(2)-layer propagation is extremely rare on the 50 MHz amateur band,
and no known occurence has been recorded on the 70 MHz band. On 50MHz
it only occurs at the peak of the solar cycle, and only then at the equinoxes
(when F-layer propagation is at best, the sun being over the equator) and
solar activity is high. Even then it seems to require chordal hops (which give
propagation at higher frequencies because the refraction angle is less) - we
know this because no stations are heard inbetween - and there is
a "sloping" ionosphere at either end of the circuit to get the signals back to
ground. The resulting contacts (last sunspot maximum) for myself were with VK
(Australia), JA (Japan), and VS6 (Hong Kong) - and I've got the QSL cards to
prove it. It is possible some transatlanic
propagation may also result from the F-layer on 50 MHz, but the majority of 
openings are multi-hop Es (see Geoffrey H.Grayer, "Sporadic E and 50 MHz
Transatlantic Propagation during 1987"; Ham Radio Magazine July 1988, p.10
et seq.). 
There is also a phenomenon known as trans-equatorial propagation, which
takes place
via the F-layer, and is relatively common on 50 MHz, but that's another story!
                                              Geoff.
**************************************************************************

Regular E does not get up to 144MHz even at solar max.
Tropo-ducting (not related to solar) does.
So, you need your ear on to sort it all out! At least here in Europe
we have the advantage that to hear a Polish or an Italian voice we
instantly know that there is odd propagation !
Malcolm runs for cover as a group of Quebecois throw things at him :-)

So, monitor the 50 or 144 MHz amateur bands and if loadsa folk start
yelling you know sumat is about !
The sporadic-E itself does not make a noise(interference).
I think you need to be more specific about the type of awfulness !
What exactly are you hearing that is bloting out your meteor reflections?

Malcolm.

****************************************************************************
Malcolm omitted to say that Es is essentially a summer-time phenomenon, although
there are some events occuring in mid-winter (spill-over from the other 
hemisphere? - I am invesigating this one). The occurrenceof Es rises rapidly 
during May to reach a peak at the beginning of June, then reduces gradually
through
June, July, and August.       

METEORS and SPORADIC E
I hope this has been of some use, and has more relevance to meteors than you
might
first think, since meteoric debris probably fuels the Es clouds, which are
made up
of heavy-metal ions. The direct causal effect of meteors forming Es is still
contraversial - my own correlation analysis of meteor showers and Es
openings on 28
MHz suggests no direct causal effect, a view which seems now to be supported
by the
majority of serious investigators.

A final note - my interest in radio propagation stems entirely from my
interest in 
amateur radio, I have no professional connection with this subject. The same
goes for
my interest in astronomy and meteors.

Hoping for many Es openings this year, and Clear Skies for all!     Geoff.
****************************************************************************
*********



*******************************************************************************
* Dr Geoffrey H Grayer			E-mail: g.h.grayer@rl.acdot uk	      *
* Room G11, Bldg R66			Tel (Office): 	(0/+44) 12 35 44 65 11*
* Detector Group			Tel.(My Lab.):	(0/+44) 12 35 44      *
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* Chilton, DIDCOT, OX11 0QX, UK 	Radio call:	G3NAQ (UK), AE4PI(USA)*
*******************************************************************************

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