Received-SPF: neutral (google.com: 195.171.43.25 is neither permitted nor denied by best guess record for domain of owner-rsgb_lf_group@blacksheep.org) client-ip=195.171.43.25;
From: "hvanesce" <hvanesce@comcast.net>
To: <rsgb_lf_group@blacksheep.org>
References: <BLU180-W3599B1565E284475140856AC880@phx.gbl> <2662DF5AA7FA416CBB09CDB90BBFF7B1@White> <016101cf39df$4f4c89a0$ede59ce0$@comcast.net>,<FA723BF050144798AD076EB0C9190D21@White> <BLU180-W432C6E6C028F0DD53D7014AC8B0@phx.gbl> <01dc01cf3a3f$86997bb0$93cc7310$@comcast.net>,<A47BA5540C3B42619C724008CDF3A0ED@White> <BLU180-W23A00B5028E9D0DEEF6B3AC8B0@phx.gbl> <2FC5CAB271A6437CB35A5B100185CEDA@White> <025101cf3a52$e0925750$a1b705f0$@comcast.net> <7DB9DD5669FC4C648838510DCAC08AFB@White> <531A506E.9040103@abelian.org> <531A5C19.9060209@abelian.org> <02ba01cf3aa3$debaad50$9c3007f0$@comcast.net> <531AF126.2060600@abelian.org>
In-Reply-To: <531AF126.2060600@abelian.org>
Date: Sat, 8 Mar 2014 04:51:15 -0700
Message-ID: <02cd01cf3ac4$bfbcdba0$3f3692e0$@comcast.net>
MIME-Version: 1.0
Thread-Index: AQFwHFQtNP1cuGk4XhlGVCAC9znl2gG7rsFSAR0lnQgBd+LZewJLh/X8Ab8nTT4C/5bZTAGUATieAUzcPSMBZtiUawDaWzx3AoAxwksBwVpScwI72uscAimolEeazCP9oA==
Content-Language: en-us
Subject: RE: LF: Daytime 29.499 kHz
Content-Type: text/plain;
	charset="us-ascii"
Content-Transfer-Encoding: 7bit
Sender: owner-rsgb_lf_group@blacksheep.org
Precedence: bulk
Reply-To: rsgb_lf_group@blacksheep.org

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: owner-rsgb_lf_group@blacksheep.org
[mailto:owner-rsgb_lf_group@blacksheep.org] On Behalf Of Paul Nicholson
Sent: Saturday, March 8, 2014 3:30 AM
To: rsgb_lf_group@blacksheep.org
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
--