Propagation News – 24 December 2023

We filed last week’s GB2RS propagation report and, shortly after, we had the biggest X-ray solar flare event this cycle!

This just shows how hard it is to predict solar activity and why long-term HF predictions are problematic. Anyway, back to the solar flare which occurred at 1702UTC on the 14 December. This was an X2.8 event that was also responsible for a coronal mass ejection.

Luckily, the Sun had already set in the UK but if, you were working the USA, Caribbean or South America on HF, you may have found the path suddenly disrupted. If that did happen to you, please let us know.

The full halo coronal mass ejection, or CME, that followed headed mostly to the west, although a glancing blow was predicted to hit us on the 15 or 16 December. It eventually hit late on the 17 December, pushing the Kp index to six on the morning of the 18 December. HF conditions remained fairly unsettled after that.

Next week, NOAA predicts that the solar flux index will be in the 140 to 150 range again and that the Kp index will be no more than two. However, that geomagnetic prediction may be wishful thinking. There are a lot of sunspots at the moment and active region 3529 may be a strong candidate for flare and CME action over the coming week.

So, our message is: work the DX when you can and don’t ignore the lower bands, such as 40, 80 and 160 metres, which may offer some good DX at night in the middle of winter.

VHF and up

The weather pattern over the Christmas period is set up as a teaser between very mild, and cold enough for some wintry weather. However, it probably won’t be cold enough – except in the north – to get too excited before the 25 December.

To set the scene and give you a chance to ‘roll your own forecasts’ in view of the long lead time for this forecast, the atmosphere is part way through its normal transition from summer-time Atlantic jet streams over Iceland to winter jet streams over the Mediterranean.

We are currently in the middle, and this puts the main jet stream path across the British Isles. It will produce alternating periods of mild and cold weather – very difficult to pin down even a few days ahead, let alone into the New Year!

What we can get from this, in terms of propagation, is a good chance of the meandering jet stream being able to invoke a mid-winter Sporadic-E event for some of us. However, the times are less predictable than in the summer, so just keep a listen out on the 10m and 6m bands for activity, it would be a shame to miss any.

Tropo has done well over the last weekend, so a large high to the south of the UK, over the continent, is worth looking out for and especially paths south to Iberia or east to the Baltic.

Lastly, look out for the lesser modes of scatter from rain or meteors, which will continue to be a random option, as well as the potential for aurora.

For EME operators, Moon declination is positive and rising, reaching a maximum on Boxing Day. Path losses are rising to a maximum on New Year’s Day. 144MHz sky noise is moderate all week.

Finally, a big thank you from the propagation team for the ‘fine business’ effort you all put into getting on the bands to explore and report these exciting propagation modes… Merry Christmas!

Category: GB2RS Propagation News