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Date: Thu, 8 Mar 2012 22:05:50 +0000 (GMT)
From: ALAN MELIA <alan.melia@btinternet.com>
To: rsgb_lf_group@blacksheep.org
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Subject: Re: LF: What say the Propagation Gurus?
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Hi Stefan, No generally a geomagnetic event is a collision with a plasma cl=
oud. If it "reconnects" i.e its field is southward pointing, Alarge number =
of hot ions and electrons are injected into the ring current (van Allen reg=
ion) these gradually leak/diffuse into the ionosphere and have the same eff=
ect as daytime photo-ionised electrons.....they absorb RF. They are much ho=
tter (higher energy....velocity) than the photo-ionised electrons so they l=
ast all night too. the result can be an extra roughly 12db per hop (approx =
2000km) So it tends to wipe ot DX.=0A=0AThe good condx do not reappear when=
 the Kp returns to normal because rge ring current acts as a reservoir of t=
his charge and it "leaks" into the ionosphere at the strained/distored edge=
 of the magnetoshere at the dawn edge. The Dst index is a measure of the ma=
gnetic field at the equator due to this circulating trapped charge. So the =
index acts like a fuel gauge indicating the quantity of trapped charge left=
. rop conditions at LF will be affected until the index rises to -20nT (nan=
oTeslas). this can in the event of a massive event take up to a month thoug=
h odd days toards the end of the period may be better than others. =0A=0ASh=
ort, one hop, paths will only see a slight effect. the attenuation is cumul=
ative every time the signal needs to execute an ionospheric "bounce". My em=
pirical "feel" for this is that it can be of the order of 6 to 12dB extra a=
ttenuation per "bounce". Hence only a slight reduction of signal on the TF =
grabber=0A=0AThe effect of signal attenuation after a mag storm is well doc=
umented in professional papers including many by Jack Belrose VE2CV ....a g=
iant in this area. It was only recently with satellite measurements that th=
e reasons began to be understood. I caught up with this due to a contact in=
 NASA. =0A=0AIt is a very complex situation, that I dont pretend to fully u=
nderstand.....but no-one has cuffed me round the ears and said "That's not =
how it is"......with data to prove it....yet. So I keep sticking my neck ou=
t :-))=0A=0AThe thing is thanks to many of the reports and help I have had =
from the LF gang .......I can say ..."it seems to work" as a hypothesis (I =
wouldn't dare call it a theory)=0A=0Ahttp://www.alan.melia.btinternet.co.uk=
/latest.htm is I am afraid out of date at the moment but there are lots of =
useful URLs=0AAlan G3NYK=0A=0A=0A=0A--- On Thu, 8/3/12, Stefan Sch=E4fer <S=
tefan.Schaefer@iup.uni-heidelberg.de> wrote:=0A=0A> From: Stefan Sch=E4fer =
<Stefan.Schaefer@iup.uni-heidelberg.de>=0A> Subject: Re: LF: What say the P=
ropagation Gurus?=0A> To: rsgb_lf_group@blacksheep.org=0A> Date: Thursday, =
8 March, 2012, 20:26=0A> Hi Alan,=0A> =0A> What do you think, could the hig=
h geomag activity be an=0A> improvement for the parth DL-> VK/ZL? The path =
has a=0A> bearing of 79 deg from here, so maybe its good that the=0A> signa=
ls coming through the auroral oval are well=0A> attenuated.=0A> This is the=
 path DK7FC -> VK1SV: http://no.nonsense.ee/qthmap/?qth=3DJN49IK&from=3Dqf4=
4mt=0A> =0A> 73, Stefan/DK7FC=0A> =0A> Am 07.03.2012 16:11, schrieb ALAN ME=
LIA:=0A> > Sorry for letting you all down......after all those=0A> quiet pe=
riods just as things get interesting, I have had a=0A> major PC crash and h=
ave not rebuilt that machine=0A> yet(Idleness rules!). It has my html edito=
r and images on=0A> it. I am keeping tabs on things with a notebook.=0A> > =
=0A> > Unfortunately I dont have all the "research" bookmarks=0A> on this m=
achine. The SWPC warning email suggests a Kp of 6=0A> from the first storm =
but I believe there may be a bigger one=0A> on the way( arrive thursday nit=
e or friday ). There is the=0A> possibility that the effects will be additi=
ve leading to a=0A> prolonged period of poor conditions.=0A> > =0A> > The s=
tate of the recovery is best indicated by the Dst=0A> index, and the rate i=
t is returning towards -20 nT. I would=0A> not be surprised if conditions w=
ere down for around 3 weeks,=0A> with localised better days in the lst week=
. The consolation=0A> is that daytime propagation my improve for a couple o=
f days=0A> after the mag storms, but it will never be better than the=0A> n=
ight-time conditions.=0A> > =0A> > Alan=0A> > G3NYK=0A> >=A0 =A0 =0A> =0A>