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From: "Alan Melia" <alan.melia@btinternet.com>
To: <rsgb_lf_group@blacksheep.org>
References: <4F1DC805.9000808@iup.uni-heidelberg.de>
Date: Tue, 24 Jan 2012 00:08:18 -0000
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Subject: LF: Re: Very special condx over the pole?
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Hi Stefan increases auroral activity leads to a big increase in noise at
high latitudes, what may be more difficult is that there has been a proton
event which have was active from about Thursday last week and was just dying
away yesterday. The M9 flare this morning produced a huge proton event one
of the biggest I have seen for ages. These proton events are assocated with
Polar Cap Absorbtion (PCA) and as Laurence knows (and bemoans) this will
wipe out LF polar routes for some time.

The auoral curtain is always there (somewhere) and it is possible we believe
to bounce under it. So if the path is such that the ground reflection is
under the curtain rather than in the ionosphere, signals may get through.
This means if you are inside the curtain then you need to be about 2000km
from the opposite side for the signal to get out.

The so called "large" geomagnetic event isnt that large (!) it was a Kp=5
minor storm rating and only just. Most of the activity was Kp=4. The Dst was
depressed to -55nT but the Ring Current was quite depleted anyway and the
Dst has already risen to -28nT (above -20nT is "good" )  This is a diffusion
process so is exponential. I guess propagation tonight and tomorrow will be
depressed but I think we then have to wait to see the effect of a CME that
was associated with this morning's M9 flare this could be much bigger and my
be more Earthward pointing. At present the Amination suggests again we will
miss and direct hit and see a glancing blow from the shock front. This may
give a major storm (Kp =6 or 7) which would depress LF propagation for a
further week or 10 days.

Not all activity is bad because very long very quiet periods lead to
depressed signal levels too. I tend to think of this as an increased "leak"
from an under-ionised E-layer but I could be very wrong in my
hypothesis.....no one has taken me to task on it yet so I keep sticking my
neck out :-))

Alan G3NYK
----- Original Message ----- 
From: "Stefan Schäfer" <Stefan.Schaefer@iup.uni-heidelberg.de>
To: <rsgb_lf_group@blacksheep.org>
Sent: Monday, January 23, 2012 8:50 PM
Subject: LF: Very special condx over the pole?


> Laurence, Alan, Scott, Jack, Steve, LF-experts... :-)
>
> Yesterday the K indes rised to above 5 so i think we hardly can expect
> "usual" propagation over the pole to AK or VE7.
>
> My question is if there have ever been unusual propagation effects been
> observed, during very strong geomagnectic activity. Things like Aurora
> on VHF or a duct for LF?
>
> The pole and what happens there in the auroral oval is an interesting
> imagination. I think (not being a propagation expert) it is always worth
> watching and transmitting.
>
>
> 73, Stefan/DK7FC
>