By Courtesy of the Propagation team
G3YLA JIM
G0KYA STEVE
G4BAO JOHN
Its all about the weather
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Jim Bacon G3YLA
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and Nick Henwood
RSGB President.
Propogation News
14th November 2025
HF
3
Last week saw one of the most dramatic auroral events of this solar cycle. Three X-class solar flares, which sparked coronal mass ejections, joined together to give us a peak Kp index of 8.67, with a solar wind speed in excess of 950 km/s.
The result was extensive visible aurora in the U.S. and Canada, although clouds prevented much of its visibility in the UK. The good news from a radio point of view was that the solar wind’s Bz or interplanetary magnetic field mostly pointed north or was neutral in the latter stages, which saved Earth from a lot of its effects.
The next day, HF propagation appeared to be almost normal with MUFs over a 3,000 km path still exceeding 24 MHz at times. By Thursday the 13th, it was mostly over 28 MHz, although there were times it dropped dramatically, and signals were weak and watery at best.
You could tell that there had been some disruption to HF by a lack of “spots” on the CDXC Slack group. While Stan ZL7/LZ1GC on Chatham Island had been spotted on the 11th, there was very little to report the next day as the Kp index rose to five.
Next week, NOAA predicts that the solar flux will remain in the range 160-170, but we can expect a repeat of unsettled geomagnetic conditions this weekend, possibly due to a large coronal hole that became Earth-facing on the 13th.
Likewise, the 20th and 21st may be unsettled, with a predicted maximum Kp index of four. After the following weekend, we can also expect more unsettled conditions, especially around the 24th to the 27th, which could see the Kp index rise to five or even more. Expect decreased MUFs and less HF activity if this is the case.
VHF and up
The current spell of unsettled weather is likely to continue into the coming week.
High pressure is always being kept at arm’s length, so there is no real Tropo flavour to proceedings. The rain prospects are very strong with, if anything, too much rain in some areas and during next week colder northerly air will mean that some snow is possible on northern hills. So there remains a possibility of rain scatter on the GHz bands.
After the recent auroral activity, the prospects are worth considering, although it would be surprising if a repeat of the exceptional event of last week were to happen. Nonetheless, stay alert to the Kp index going above Kp=5 and check for activity on 10m, 6m, 4m and 2m. The event of last week was triggered by three successive days of X-class flares so, for an early ‘heads-up’, start with the Sun.
The foEs graphs on www.propquest.co.uk are interesting for the evening of the last Autumn Series contest on 12th November and would have caused some rapid changes in propagation as paths were affected by the F2-layer one minute and Sporadic-E the next.
It is occasionally worth examining the graphs now and again to relate perceived conditions from the radio speaker to actual measurements of the ionosphere. Of course, the data from Dourbes is not necessarily what would have been recorded over the UK, but it gives a good flavour, and the takeaway message is that although we think of Sporadic-E as a summer phenomenon, it can play a role outside the main season.
Meteor scatter is certainly in the frame this week since the Leonids meteor shower peaks on Monday 17th November, and since meteors also play a part in Sporadic-E , it’s another reason to check the foEs graphs for out-of-season activity.
For EME operators, the Moon’s declination goes negative again on Saturday, so Moon window lengths and peak elevation fall accordingly. Path losses are increasing to a maximum at apogee on the 20th. 144 MHz sky noise is low all week except for the whole of Thursday, when the Sun and /Moon are close in the sky.
G3YLA JIM
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G0KYA STEVE
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