Alan
Thanks for the update and insight.
Absolutely no trace of Stefan's signal in CT last night. A few nights back he was 25+ dB s/n (in 28
mHz). Long distance VLF signal levels below normal as well.
Jay W1VD WD2XNS WE2XGR/2
----- Original Message -----
From: "ALAN MELIA" <[email protected]>
To: <[email protected]>
Sent: Friday, March 09, 2012 5:57 AM
Subject: Re: LF: Big solar flare - major geomagnetic storms to follow
Hi all more geomag storming this morning. It looks as though I might have got my timing wrong.
However the 56 hours to the Kp=7 event is a bit slow for such a big event, and the predicted speed
of that CME.
I suspect this mornings event may be what I refered to yesterday as a "sub-storm". This occurs when
the plasma cloud sweeps past Earth and some is then trapped in 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 the Sun-spots this strain is relieved as the field snaps back into a lower energy state.
The excess energy which is released as the field collapses is transfered 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 the shock
of that plasma "bullet" arriving. I believe this mornings event may have been of this nature.
How 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-layer.
There is some discrepancy between the Dst estimates. The Colorado estimate is running at about -50nT
whilst the Kyoto value is around -150nT. Kyoto is based on a number of ground located magnetometer
observations and is prone to rather wild fluctuations, and often "overshoots". The Colorado plot 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.
Overall I think this indicates a mild 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 as it returns to
around -20nT....the indication of quiet, good propagation conditions. Just before the conditions
settle there can be some exceptionally good nights, probably caused by favourable fading/multipath.
These are very location dependent and do not work for everyone.
However keep watching..... NOAA predict the possibility of more X-Class flares from the current
spots, with the associated CMEs.
Good LF DXing !!
Alan
G3NYK
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