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Re: [IRCA] the big black absorptive cloud
Thank you. Joking about conditions can be dangerous sometimes! Oh yes,
midwinter anomaly was a big problem last winter and some winters, too.
Hopefully this winter will be better. But maybe today this was still
something more short-term: the K index also dropped to at 15 UT and there
was an aler from NOAA at 0500:
ALERT: Electron 2MeV Integral Flux exceeded 1000pfu
Threshold Reached: 2007 Nov 03 0500 UTC
Observed Yesterday: Yes
Yesterday Maximum 2MeV Flux: 4620 pfu
73, Mauno
----- Original Message -----
From: "Nick Hall-Patch" <nhp@xxxxxxxx>
To: "Mauno Ritola" <mauno.ritola@xxxxxxxxx>; "mailing list for the
International Radio Club of America" <irca@xxxxxxxxxxxxxxxx>
Sent: Saturday, November 03, 2007 6:50 PM
Subject: Re: [IRCA] the big black absorptive cloud
> At 14:40 03/11/2007, you wrote:
>>Hi Nick,
>>where do you find info about this cloud? I also noticed the same
>>wipeout here. Everything looked excellent still at 1200.
>
>
> I wish I knew, Mauno; I was joking at the time, but it seems to be a
> very real phenomenon, and one which, to my limited knowledge, still
> doesn't really have an observable solar / geomagnetic parameter
> associated with it. What has changed since a day or two ago which
> has caused all long distance signal strengths to deteriorate so markedly?
>
> (forgive me, as I suspect you already know all the following) This
> deterioration (not always so sudden as today) was I believe initially
> described as the "mid-winter anomaly" in DX club literature in the
> sixties, and was applied to the general drop off of trans-Atlantic
> signal strengths observed as mid-winter approached, after the glory
> days of September and October. This is an unfortunate term, because
> the same term is also used in academic literature to describe a
> daytime phenomenon of winter-time excessive absorption of signals in
> the D region, which doesn't seem to carry over to night, at least
> according to theory; I don't think I've ever seen empirical data on
> this. To confuse the issue further, there also appears to be
> something called a "winter anomaly" associated with the F2 layer, and
> they don't appear related.
>
> At one time, some thought stratospheric warming was associated with
> this, but Carl Leutzselschwab, K9LA, the 160m propagation expert,
> pretty much debunked that in a couple of articles.
>
> I banged on about the MWA a couple of years back on the
> coastalroundtable group, but didn't get much interest at the time
> from other than John Bryant. There are a number of references on the
> daytime winter anomaly, which you probably already have, but
> nighttime winter anomaly conditions on medium wave just don't seem to
> have been researched particularly so far as I can tell. So we're
> left with my not so mythical "big black absorptive cloud".
>
>
>
> best wishes,
>
> Nick
>
>
>
>
>
>
>
>
>
>
>>I received this from NOAA:
>>Space Weather Message Code: ALTEF3
>>Serial Number: 1397
>>Issue Time: 2007 Nov 03 0505 UTC
>>ALERT: Electron 2MeV Integral Flux exceeded 1000pfu
>>Threshold Reached: 2007 Nov 03 0500 UTC
>>Station: GOES12
>>Observed Yesterday: Yes
>>Yesterday Maximum 2MeV Flux: 4620 pfu
>>
>>73, Mauno
>>
>>----- Original Message ----- From: "Nick Hall-Patch" <nhp@xxxxxxxx>
>>To: "Mailing list for the International Radio Club of America"
>><irca@xxxxxxxxxxxxxxxx>
>>Sent: Saturday, November 03, 2007 4:22 PM
>>Subject: [IRCA] the big black absorptive cloud
>>
>>
>>>
>>>> As for this morning, don't ask! A COMPLETE wipe-out. Not a
>>>>single audio heard between 13:47 and 14:05....first time this
>>>>season. Doesn't look good, I'm afraid! ...........Walt.
>>>
>>>Glad it's not just me. I shouldn't have mentioned that (not so
>>>mythical?) absorptive cloud in the ionosphere, because it seems to
>>>have arrived over the Pacific Ocean this morning, there being no
>>>indication of geomagnetic activity on the NOAA site, just K-indices
>>>of zero and one overnight.
>>>
>>>audio traces on 612, 747 and 774 by 1420UT, just a few weak
>>>carriers otherwise.
>>>
>>>Nick
>>>
>>>
>>>
>>>
>>>****************************************************************************
>>>Nick Hall-Patch
>>>Victoria, B.C.
>>>Canada
>>>
>>>****************************************************************************
>>>
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>>>
>>>
>
> ****************************************************************************
> Nick Hall-Patch
> Victoria, B.C.
> Canada
>
> ****************************************************************************
>
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