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Re: LF: Best results so far from Germany to Tasmania

To: <[email protected]>
Subject: Re: LF: Best results so far from Germany to Tasmania
From: "Markus Vester" <[email protected]>
Date: Wed, 10 Apr 2013 08:40:54 +0200
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Alan, thanks very much for the detailed and interesting explanations! One thing I have always found hard to grasp was that charges can be stored up there for as long as several days. But it seems the clue is just the extremely low gas density, providing the ions with a long mean lifetime between collisions and recombinations. 
 
As you say, Loran was nonexistent anywhere south of Saudi Arabia (at least in this century), and of course in 2010 American activity has ceased except for a few sporadic tests. From watching the traces I sometimes got the impression that when on above-average propagation existed from east Asia, the maximum enhancement from America tended to occur one or two nights later. But this was just a subjective notion, and I should some day try to prove it by plotting hard data on fieldstrength etc.
 
Best 73,
Markus

From: Alan Melia
Sent: Tuesday, April 09, 2013 10:50 PM
Subject: Re: LF: Best results so far from Germany to Tasmania

Hi Markus, it would seem that the majority of the "hot" precipitated electrons enter the ionosphere at the dawn and dusk edges where the magnetosphere is distorted by the solar wind pressure. I believe they enter at high latitudes and diffuse towards the equator. So I am guessing that if there are any gradients they are pole towards the equator. Certainly there is evidence from Laurence and Scott VE7TIL that they see propagation collapse almost immediately after a geomag shock. I dont have any data for worldwide distribution. In fact the only plottable data is that for the N.Atlantic path to CFH. The plots from Scott suggest that the decay of the attenuation after a shock is around 5-6dB/hour . This suggests that when the Equatorial Ring Current is exhausted  the global ionosphere returns to the simple photo-dissociation model with solar UV activation (what a load of pretentious rot I just wrote :-))  ) I mean we get an absorbing daylight D-region again which disappears as soon as it becomes dark. The solar eclipse plots of a few yeas ago suggest the free daytime electrons recombine in seconds due to the relatively high pressure 50 to 100km altitude (it would still make you gasp a bit though :-))  ) and their relatively low energy (just above the ionisation level)
 
I wonder if your Loran data would give any information on worldwide distribution? However I believe most of the Loran chains are in the Northern Hemisphere (not sure if there are any around VK/ZL
 
The Dst is not a measure of electrons in the D-layer, rather it is a measure of the potential gradient driving the exchange between the Ring Current and the Ionosphere . Thus very low Dst indicates a high potential to drive lots of excess free electrons into the D-region. The Dst recovery as the ring is depleted is approximately logarithmic as one would expect for a diffusion process. I did wonder whether measurements of total electron density would give any ideas. but I could not make any progress with that, probably because most of the electrons will be in the higher levels of the F-layer.
 
Interestingly when a big storm occurs the excess electrons have the same effect as a flare in daytime ! They enhance the daytime signal level for one or perhaps at most two days. The are much hotter that the flare generated electrons so the effect lasts longer but is much weaker than the absorption effect at night.
 
We may get some more ideas when the data from the latest satellite (that found the 3rd Van Allan belt) finishes surveying the region. I have seen it suggested that there are up to 7(I think it was) ion filled rings reaching up to nine Earth diameters out.
 
Unfortunately a good Dst doesnt guarantee good signals.....there is something else at work. It may just be multipath but I cant get any useful data yet. Maybe I need phase data.
 
Best Wishes
Alan
G3NYK
 
----- Original Message -----
Sent: Tuesday, April 09, 2013 7:49 PM
Subject: Re: LF: Best results so far from Germany to Tasmania

Edgar, Stefan,
 
this is an outstanding result! Great to see what is possible on LF, given a good antenna, a quiet location, and patience paired with persistence.
 
Did you by chance have a look at the best SNR in the spectrum plot? The fat parts of the trace might have been 12 or even 15 dB, in a 7.5 mHz FFT. This would put it within easy reach of an Opera-32 correlation detection, and possibly even close to a WSPR-15 decode.
 
Alan, I assume that DST would affect attenuation globally, without preference for one direction or another. Or could an eastern path be better during one night, versus westward in another?
 
Best 73,
Markus (DF6NM)
 

Sent: Tuesday, April 09, 2013 2:09 PM
Subject: LF: Best results so far from Germany to Tasmania

LF,

Last evening there was excellent LF propagation from EU to VK. Edgar J. Twining (SWL) was watching the LF DX window for several weeks now. The season on that path in spring (EU) 2013 was very poor and we already thought that the season is over. However yesterday the path was open for a exceptional long time and the S/N was very good! Transmissions were done in DFCW-180. I've been on air for several days now and such a result is most probably possible for 1 time in the year or maybe 2 years.

These are the results:
My signal: https://dl.dropbox.com/u/19882028/LF/DK7FC%20WR%20ver%20spectrum%20-18.PNG
DCF39: https://dl.dropbox.com/u/19882028/LF/DCF39%20WR%20ver%20spectrum%20-14.PNG
DCF39 plot: https://dl.dropbox.com/u/19882028/LF/DCF39%20WR%20ver%20plot%202013-04-08%2021-30.jpg

The path is 16806 km, http://no.nonsense.ee/qthmap/?qth=QE37PD&from=jn49ik00wd

It shows once again that it is always worth to transmit and to receive/watch for exceptional conds(x) on the bands!

Many thanks to Edgar for his continuous patience and interest to receive on 137 kHz from the other side of the world!

73, Stefan/DK7FC
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