From: "M. Sanders" <misan@xs4all.nl>
To: rsgb_lf_group@blacksheep.org
Subject: LF: RE: Solar Flare on LF...
Date: Mon, 16 Aug 1999 22:05:07 +0200
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Hi All

This effect is als known as the Moegel-Dellinger effekt or SWF (Shorwave
Fade Out). A German language description can be found in the Rothammels
Antennen Buch chapter 2.3.2.2. Ionosphaerenstoerungen. This text confirms
the effect as a D-layer disturbance caused by solar flares. The intense
radiation increases the ionisation in the D layer. The HF radio signals do
not reach the E or F layers due to increased absorption (fade-out). The LF
signals increase as they reflect better against the bottom of the D-layer
when the refraction index (ionisation density) increases. The same physics
apply to LF/HF as to visible light. Chaos theory and the behavour of other
gasses (water-vapour, ozone etc) in the earth atmosphere make it hard form
me to beleive the D or E layers are homogeneous. This may account for
'local' observations, measurement variations as well as different effects at
different observation distances. Short distances observe mainly groundwave
effects and there is a minimum distance for the 'first-skip' from refelction
against the D layer. The minimum skip distance is a measure for the hight of
the D layer and the refraction index. There is a poor reflection at a high
angle.

Looking at the data collected during the eclipse on the internet pages gives
food for thought!  May be there have been made recordings of some more
'anomalities'? I have received HBG75 eclipse measurement data from other
amateurs. Will put some combined graphs and an analysis on my homepage soon
and ask for comments via the reflector.

Does anyone have information about the temperature effect from an ecliipse
observed in the ionosphere between 50km and 150km hight?

73's

Michael Sanders, PA3BSH
mailto:pa3bsh@amsat.org


> -----Oorspronkelijk bericht-----
> Van: majordom@post.thorcom.com [mailto:majordom@post.thorcom.com]namens
> Peter W. Schnoor
> Verzonden: maandag 16 augustus 1999 17:53
> Aan: rsgb_lf_group@blacksheep.org
> Onderwerp: LF: Solar Flare on LF...
>
>
> Hello Group,
>
> Recording HBG75 (75 kHz) over the whole last week I found a
> strong anomaly at Saturday, 14th. I observed a steep
> increase of field strength (9dB) followed by a smooth
> decrease looking like a typical exponential function.
> Looking to sites offering geomagnetic data I could not
> explain it. So my first assumption was that it could have
> been an artefact.
>
> Expanding the graph to higher zoom level showed the typical
> weak 60sec. rhythm of HBG due to my short integration time
> in front of the A/D-Convertor (time constant 2.6sec.). So
> I'm sure that it was the signal of HBG and not any kind of
> noise source.
>
> J.J.Delcourt from RMI gave the explanation: It was the
> influence of a Solar Flare on LF propagation. (Thank you!) I
> never observed this before...
>
> A plot of this event can be found there:
> ftp://ftp.rz.uni-kiel.de/pub/nephro/nephlab/lp/solarflare.gif
>
> 54°16'N / 10°04'E, JO54ag
> 73 es gl de Peter, DF3LP
>
>