Paul,
Thanks; as always, great data and analysis.
After reviewing the six (including 1 previous) plots, I scrolled back and
forth through them; in sequence they make a compelling picture.
The prognosis for 29 kHz activity is quite interesting; I'm looking forward
to bringing equipment online. At the moment I am surrounded by 29 kHz TX and
RX equipment that almost works.
73, Jim AA5BW
-----Original Message-----
From: [email protected]
[mailto:[email protected]] On Behalf Of Paul Nicholson
Sent: Saturday, March 8, 2014 3:30 AM
To: [email protected]
Subject: Re: LF: Daytime 29.499 kHz
Yes Jim the 'z' scale is proportional to amplitude (flux density), not
power.
I completely agree with your interpretation of the plot -
- The nighttime window doesn't quite close and even
in high summer we still have couple of useful hours.
- In compensation for the short night, the daytime propagation
improves: better and longer, and by July, midday levels
are about 6dB below the March nighttime.
We should consider 'midday' to be relative to the center of the path.
For comparison, NAA for two more years
http://abelian.org/vlf/tmp/naa_2012a.png
http://abelian.org/vlf/tmp/naa_2011a.png
Looks pretty repeatable year to year.
As Alan mentioned, the midday 'dome' is a feature of most long
range diurnals. For example, NAU (Aguada) at 40.8 kHz for
2012 and 2013
http://abelian.org/vlf/tmp/nau_2012a.png
http://abelian.org/vlf/tmp/nau_2013a.png
Path length to NAU is 6740km, NAA is 4672km.
Going eastwards, TBB (Bafa, Turkey) on 26.7 kHz range 2883km
http://abelian.org/vlf/tmp/tbb_2013a.png
shows that it's not just an east-to-west feature.
During flares, the signal is always enhanced which confirms that the dome
improves with ionisation.
The midday dome is essentially D-layer propagation. D-layer is formed by
solar radiation (mostly nitric oxide ionised by Lyman
alpha) with a reflection height of around 70km. At night this
layer dissipates and reflection occurs from the E-layer at
95 km or thereabouts. Away from midday we have a mixture of the two, with
E-layer reflections being attenuated by passage through a partially formed
D-layer.
The D layer is a good reflector when fully formed but being lower, more hops
are required to cover a path.
--
Paul Nicholson
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