[Lf] Transatlantic Conditions

[Andre' Kesteloot]

Alan Melia wrote:

> Hi All, as John is back on the other end again, I thought maybe I ought to
> post an opinion about the conditions at present.
>
> We had a monumental series of X-ray flares on 24 and 25 of Nov. These
> 'wiped' the band for quite a while with lots of heavy absorption. (I think I
> am beginning to get a handle on these events now) I have also been reading a
> lot of references, and I now realise that the band conditions do not follow
> in line with the K index as we at first thought. It tends to start that way
> with a slight lag of maybe 24hrs, but the injected particles from CMEs or
> Coronal Hole events seem to hang around for a lot longer than the K index
> shows a disturbed geomagnetic field. (The K index is a magnetometer
> measurement of the the geomagnetic field disturbance, whilst the radio
> conditions are dependent on the injected particles from the event and their
> decay rate) We only started to come out of the absorption mid last week, as
> the path went into 'violent-fade routine'. Very deep dips, but on Wed night
> the highest peak I have seen in the logging project so far, and probably
> lasting for almost an hour. Thursday CFH was off air, and Friday was not
> spectacular here, though the plot did reach about 45dBu between 0100z and
> 0200z. Saturday night produced some sustained high levels, with 40dBu
> between 2330 and 0100z. The levels were well above 30dBu for most of the
> night, probably averaging 35dBu, with several peaks to 39dBu. This is the
> right kind of territory for a successful trip across to John from out
> previous experience.
>
> The state of the path will return slowly to 'normal', which is distinguished
> by the lack of any deep or 'rapid' (30min cycle) fading, unless we are hit
> by any further particle streams. the average level for these stable periods
> is 32-34dBu just about possible for a station with a good take-off and the
> full 1W ERP.
>
> Just a warning....the fading times shown on my graphs are a function of my
> geographical position. They will differ for anyone further away that 25kms
> from me. Also the coincidences may not be the same. I may not see a full 6dB
> enhancement that you see, and you may not see the same picture as I do. So
> it is worth plugging away during these conditions, monitor 137.00 if you can
> during your breaks, and note CFH strength. Dont be disheartened if it is
> down, it can climb 20dB in a little as 10 minutes under these unstable
> conditions.
>
> So far the most favourable conditions have seemed to occur either 24hrs
> after a big X-ray flare (just before the accompanying CME shock arrives) or
> much later as the after-effects of the disturbance die away 4 to 10 days
> after the CME impact. There are so many variables that each event is
> different in detail, although I am beginning to see a pattern.
>
> The above is my opinion, and I could just be wrong!
>
> Rik ON7YD is using up his excess holiday entitlement running up to Christmas
> so there may be some slight delays in posting the CFH plots on his site. I
> can forward a GIF file  (about 8 to 10Kbytes) as an attachment to anyone who
> wants a to look at them urgently.
>
> CFH has been transmitting just a sub-carrier on the HF sideband (about
> 137.040) for the last 3 days with no sign of 'data' or modulation. It is
> probably going through another experimental phase so may disappear at short
> notice (dont rip your RX apart if you dont hear it!!) The advantage is
> probably lower levels of sideband noise for John. SXV has moved down to the
> bottom 100Hz of the band so you will probably need to negotiate a different
> set of frequencies to those used earlier in the season.
>
> Good Luck to you all
> Cheers de Alan G3NYK
> Alan.Melia at btinternet.com