Bill W5WVO [EMAIL PROTECTED] wrote:
I've read in a number of places over the years that mid-latitude
sporadic-E propagation does seem to be inhibited by large-scale
geomagnetic disturbance, just as HF propagation is -- albeit perhaps by a
different mechanism. If the mechanism is indeed different (and it seems to
me it would almost have to be), I'm not aware of any theory on how it
might work. I have a few home-grown hypotheses on the matter, but nothing
I'm willing to admit to in public. :-) Anyone know of any science on the
relationship between mid-latitude sporadic-E propagation and geomagnetic
disturbance?
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Bill,
Although not published science (as far as I am aware) sufficient evidence
has been collected during the past 40 - 50 years to suggest that geomagnetic
disturbances do have an effect on the usual type of mid-latitude E layer hop
type propagation. At VHF a geomagnetic disturbance appears to have the
greatest effect on paths which follow lines of equal geomagnetic latitude,
apparently creating ducts which provide the means for contacts over very
long distances i.e around 2000 miles plus, without any closer signals being
heard. Auroral Es is probably one example of such propagation, which also
works at 70 MHz as some of us found out in 1970 while attempting a 4m/6m
contact across the pond when I was a VE2. The effect on paths which cross
lines of geomagnetic latitude e.g. VE2 to South America are more difficult
to assess using ham signals because of the level of activity, but
occasionally S.American comms just below 50 MHz would appear for a short
period during or after a disturbance without any sign of the 6m US ham
signals usually heard during an Es opening.
Something similar happens here on 40m with Far Eastern stations (short path)
suddenly appearing after the Europeans suddenly disappear, but this is a
rare situation.
73,
Geoff
GM4ESD
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