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Date: Fri, 9 Mar 2012 10:57:57 +0000 (GMT)
From: ALAN MELIA <alan.melia@btinternet.com>
To: rsgb_lf_group@blacksheep.org
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Subject: Re: LF: Big solar flare - major geomagnetic storms to follow
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Hi all more geomag storming this morning. It looks as though I might have g=
ot my timing wrong. However the 56 hours to the Kp=3D7 event is a bit slow =
for such a big event, and the predicted speed of that CME.=0A=0AI suspect t=
his mornings event may be what I refered to yesterday as a "sub-storm". Thi=
s occurs when the plasma cloud sweeps past Earth and some is then trapped i=
n a "magnetic bottle" in the tail of the magnetosphere. The magnetic field =
becomes highly distorted and twisted by the extra hot charge. Just as in th=
e Sun-spots this strain is relieved as the field snaps back into a lower en=
ergy state. The excess energy which is released as the field collapses is t=
ransfered to the plasma "glob". The result is that two parts of the plasma =
are fired off at very high speed. one towads Earth and one away from Earth =
(to conserve momentum....a basic law of physics). This mornings event was t=
he shock of that plasma "bullet" arriving. I believe this mornings event ma=
y have been of this nature.=0A=0AHow does it affect LF? The charge from the=
 "bullet" is injected into the ring current so tops up the charge reservoir=
, and this lengthens the period of excess attenuation in the night-time D-l=
ayer. There is some discrepancy between the Dst estimates. The Colorado est=
imate is running at about -50nT whilst the Kyoto value is around -150nT. Ky=
oto is based on a number of ground located magnetometer observations and is=
 prone to rather wild fluctuations, and often "overshoots". The Colorado pl=
ot is based on a calculation using the solar wind parameters as observed by=
 the ACE satellite. From my experience I find the latter to be more useful/=
meaningful in terms of LF effects.=0A=0AOverall I think this indicates a mi=
ld effect. Long distance night-time paths will be affected for a week or so=
. For a good indication of the progress of of the recovery, watch the Dst a=
s it returns to around -20nT....the indication of quiet, good propagation c=
onditions. Just before the conditions settle there can be some exceptionall=
y good nights, probably caused by favourable fading/multipath. These are ve=
ry location dependent and do not work for everyone.=0A=0AHowever keep watch=
ing..... NOAA predict the possibility of more X-Class flares from the curre=
nt spots, with the associated CMEs.=0A=0AGood LF DXing !!=0A=0AAlan=0AG3NYK=
=0A=0A