RSGB
RadCom Assistant Editor | November 14, 2025
Last week saw one of the most dramatic auroral events of this 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 kilometres per second.
The result was extensive visible aurora in the US 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. This saved the Earth from a lot of its effects.
The next day, HF propagation appeared to be almost normal with maximum useable frequencies, or MUFs, over a 3,000km path still exceeding 24MHz at times. By Thursday, 13 November, it was mostly over 28MHz, 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 11 November, there was very little to report the next day as the Kp index rose to 5.
Next week, NOAA predicts that the solar flux will remain in the 160 to 170 range. However, we can expect a repeat of unsettled geomagnetic conditions this weekend, possibly due to a large coronal hole that became Earth-facing on 13 November.
Likewise, Thursday, 20 November and Friday, 21 November may be unsettled, with a predicted maximum Kp index of 4. After the following weekend, we can also expect more unsettled conditions, especially around 24-27 November, which could see the Kp index rise to 5 or even higher.
Expect decreased MUFs and less HF activity if this is the case.
VHF and up propagation news from G3YLA and G4BAO:
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.
During the coming 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 5 and check for activity on the 10, 6, 4 and 2m bands.
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 propquest.co.uk were interesting for the evening of the Autumn Series contest on 12 November. There were 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.
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 is due to peak tomorrow, 17 November. Since meteors also play a part in Sporadic-E propagation, there is another reason to check the foEs graphs for out-of-season activity.
For EME operators, the Moon’s declination went negative again yesterday, 15 November, so Moon window lengths and peak elevation fall accordingly. Path losses are increasing to a maximum at apogee on Thursday, 20 November. 144MHz sky noise is low during all of the coming week except for the
whole of Thursday, when the Sun and Moon are close in the sky.
https://rsgb.org/main/blog/news/gb2rs/propagation-news/2025/11/14/propagation-news-16-november-2025/
(Mike Terry, UK/BDXC)
