Propagation News – 18 December 2022

Things hotted up last week with a healthy increase in sunspot activity. The number of sunspots ramped up, giving us a solar flux index of 165 by Thursday.

The other upside was the fact that geomagnetic conditions were quite settled with the Kp index remaining between one and three all week.

There were some downsides. We have had an increase in the number of solar flares, with a total of 14. Of these, 11 were M-class. This is all happening around active region 3165, which is now a prime candidate for an X-class solar flare, the most powerful.

There were reports of poor HF propagation on the morning of the 15 December, which can possibly be attributed to the solar flares on the Sun. The graph of the maximum useable frequency, measured at Dourbes, looks rather like a roller coaster ride, with the extrapolated MUF over 3,000km being more than 38MHz at 9.15am and below 19MHz 20 minutes later.

The moral of this story is that if HF propagation seems to fail just give it 20 minutes and see if it recovers.

According to NOAA, the high solar flux index won’t continue for much longer. It predicts that the SFI will reduce to between 115 and 120. The Kp is also predicted to stay low, at least until the 22December  when it is forecast to rise to five, possibly because of a returning coronal hole from 27 days ago.

And finally, both the Chilton and Fairford Digisondes are offline at the moment, so please select Dourbes if using Propquest.co.uk

VHF and up

The cold weather will be displaced as a temporary mild spell brings higher temperatures, plus wet and windy weather, during this weekend.

Eventually, colder westerly air with showery troughs will return from the west, but still with further bands of rain. There will probably be some good rain and snow scatter opportunities for the GHz bands. Tropo looks a bit thin, although there may be a brief enhancement on Sunday morning to France and the Low Countries but this will be gone by the afternoon.

The other modes like meteor scatter and aurora are still a consideration, but much less predictable.

With the Geminids meteor shower past its peak, there are two minor showers to look out for this week.

The Leonis Minorids are active from the 5 December to the 4 February, reaching a maximum on the 20 December with a low Zenithal Hourly Rate, or ZHR, of around five. The Ursids are active from the 17 December to the 26 December reaching a maximum on the 22 December, also with a low ZHR of around 10.

Moon declination went negative on the 17 December, so Moon windows will continue to shorten and zenith angles decrease. EME path losses are falling as we head towards perigee on Christmas Eve. 144MHz sky noise is increasing all week and on Friday we get close to an eclipse, so it will be very high during the whole Moon pass.

Lastly, to repeat the ‘heads up’ from last week about midwinter Sporadic-E, it is still worth mentioning since it usually becomes a reference after the event, and it would be nice to be there before it happens!

So, employ the usual check of HF and VHF clusters from 10 to 4m and use www.propquest.co.uk and its EPI or Es probability index plots to see where the most likely areas for Es are located.

Like summer events, rarer mid-winter Es are often associated with powerful jet streams and this unsettled weather is a good source for these.

Category: GB2RS Propagation News