Hi Mike I had been watching triggered by a comment from Steve Nichols
preparing the RSGBNews Prop report.
The Thursday geomag event was much weaker than expected I havent checked but
I suspect the IMF was in the wrong direction to reconnect and the KP=4
plasma front just bounced off the magnetosphere. there was a drop in Dst in
the early evening (-20nT), but by 00:00 UTC the Dst was up to -5nT again.
This seemed to continue through the weekend despite a number of Kp=4 events.
However Sunday produced two periods starting with Kp=5 after 00:00 and Kp=4
following at 03:00 this depressed the Dst to -40nT, over the 00:00 to 06:00
period.
Note the Azores path to Paul is far enough south to avoid the worst of the
precititation, and auroral effects. The Eu<>US paths skirt the auroral zone,
which probably extended further south on the 19th
Correlation does not relate to causation, as the statisticians say :-)) but
it is possible the build up of precipitated charge from the ring current as
enough to 'push northern TA propagation' over the edge. WSPR may be more
sensitive than say visual modes and is generally used with a lot less power
margin. I am surprised in a way that a relatively small geomagnetic event
had such a big effect, but maybe the path latitude and auroral extent
explains that.
That is the best bit of 'hand waving' I can come up with. I have previously
tried to use WSPR spots but find far too much variability in trasmissions
and receptions (local noise) to make sense of the figures. As there are
becomming more regular spotting stations it may become more useful at LF/MF,
but it entails analysing a lot of data.
Alan
G3NYK
----- Original Message -----
From: "Mike Dennison" <[email protected]>
To: <[email protected]>; <[email protected]>
Sent: Monday, February 19, 2018 11:05 AM
Subject: LF: 136kHz T/A this weekend
Interesting conditions this weekend. On Friday I received N1BUG's
133kHz WSPR2 transmissions a couple of times, on Saturday night he
came through an amazing 23 times between 2326 and 0644UTC.
But last night (Sunday) he did not appear to be received by any
European stations. Instead, I decoded one transmission by K3RWR, and
I believe I was the only European to do so.
That was quite a big change in conditions. Looking at the propagation
data at Boulder, there seemed to be no significant change that might
explain it. Do the propagation gurus have any thoughts?
Mike, G3XDV
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