The paths of Sporadic Es (Es) openings can often be seen to move across the Earth in regular patterns.
At one extreme, at higher frequencies we regularly get openings which only include one or two stations, and there is no movement discernible there. At other times especially at lower frequencies there is so much activity from multiple areas of Es that we cannot make out any detail out at all.
From time to time I find an opening which shows up the movement in a clear way. I have described two of these before on this blog -
1) here, where a 50MHz opening to Japan showed an east-west pattern at the Japan end and suggested that whatever propagation method opens this path it looks very much like Es at the Japan end.
2) here, where on 144MHz the distance of the path shortened 700km over a 22 minute period.
On 6 August 2023 there was a 144MHz Es opening which showed a definite east-west transit at GM4FVM.
As luck would have it, this was a good opening with me contacting 31 stations in 103 minutes. This covered 6 countries and 18 squares, with the best DX being IK7UXW in JN80 at 2236km. On the other hand luck also dictated that I was absent from the shack for 28 minutes roughly in the middle of the event, but this did not seem to make much difference. This time the average lengths of the paths changed very little but the azimuth angle moved steadily (roughly) from "south east" to "south south east". Overall the path traced by rotator was in an arc which headed from east to west.
I have dithered a bit over how to represent this on the blog. I have plotted graphically the azimuth (my beam direction) against the time and produced a line of best fit, but somehow the graph does not show how the Es shifted very well.
So what I have done is to show the map of the contacts with a text box showing how the front of the contacts moved across, expressed in terms of time and azimuth. The azimuth (my rotator angle) is at the top, and the time that contact occurred is below. The azimuth figures were calculated from the locators of the stations I worked.
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I have listed the contacts in two different colours - red for the first phase, blue for the second phase, and I was out of the shack in between.
The leading edge of the contacts moved from 122 degrees at 09:22 to 156 degrees at 10:33, that is 34 degrees in 71 minutes or almost half a degree every minute. In reality it was not evenly spread and at times (especially at the start and end of the event) it was moving more quickly.
The "searchlight" of Es propagation shining on the ground was tracing a path which moved past stations at a surprisingly fast rate. Generally as it moved on contact was lost with those behind, with only the odd contact in the rear of the leading edge.
During the period I was out of the shack it did not seem to move much at all. I must go back in the log and try to work out what was happening then.
It would be easy to dismiss this as an opening into Italy and France, with one contact each in Croatia, Switzerland (with a very determined 2E0 stations adding to the fun on tropo). Looking at my normal map of an opening it just looks random. However, looking at the timings the Es path seems to be moving in an organised way.
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| A more conventional view of the opening on 6 August 2024 |
When viewed in DX Maps it is possible sometimes to see areas of high frequency refraction which appear to move between squares in a westerly direction as the day progresses. I can see a similar effect in openings such as this. What the cause is could be difficult to determine. At first it looks likely that the Sun's movement relative to the Earth might be the cause. Certainly the Sun plays a part by driving the air movements which create and organise the Es layer. Ripples in the Es layer could also be a factor. However it might be more complex that that.
I wonder if this was one event or two separate ones. The fact that the propagation did not seem to move much during around half an hour when I was not in the shack might suggest that. Also, the full picture may be hidden due to the geography. Obviously there are not many stations in the Adriatic and Tyrrhenian seas. Signals from there might have given a fuller picture. Still it looks pretty clear to me that the paths were moving steadily westwards.
Here is the summary from that first map, still with the first phase in red and the second phase in blue:-
156 151 148 144 140 139 136 131 122 Azimuth
10:59 10:44 10:42 10:35 10:00 09:41 09:36 09:31 09:22 Time
More research necessary.
73 Jim
GM4FVM
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