Propagation News – 25 August 2024

We had yet another week with a high solar flux and relatively calm geomagnetic conditions.

The solar flux index ended up at 239 on Thursday 22 August, while the Kp index has been below 4 since Sunday 18 August. There are currently 11 active sunspot regions on the Sun’s surface and there is a 20% chance of a major X-class solar flare according to the NOAA Space Weather Prediction Center.

There are signs that HF propagation may be improving, but it will probably be another month or so before we see any large change. This is due to the summer doldrums that see the ionosphere harder to ionise due to a change in its chemical composition.

By mid to late September, we will start to see a change to autumnal conditions and DX will start to open up again on the higher bands. Having said that, there is still DX to be had. The N5J DXpedition to Jarvis Island in the Pacific Ocean proved that the DX is workable, but the path was mainly open to well-equipped stations with beams and linear amplifiers.

15m remains the best DX band and there are occasional openings on the 12m band. The 10m band may come into its own as we head into September and October.

According to the NOAA Space Weather Prediction Center, solar cycle 25 likely reached its highest sunspot number yet of at least 299 on the 8 August. This may increase further, but we may be close to solar maximum.

Next week, NOAA predicts that the solar flux index will remain around 200 to 210. Geomagnetic conditions will depend almost entirely on the occurrence of coronal mass ejections, or CMEs. And, as we are at a particularly active part of the solar cycle, flares and CMEs are very prevalent.

VHF and up

The overview for the coming week is that, although some fronts will affect the north and west at times, there are only a few that reach down to the southeast of Britain. This means that rain scatter is more likely in northern areas.

There will be weak high pressure over southern areas for much of the coming week and, although not enough for a full-blown Tropo event, conditions should be a little ‘up’, especially for paths into the near continent or across the North Sea.

Meteor scatter is back to a more random approach since the broad peak of the August Perseids comes to an end. The solar conditions mean that auroras can be a possible element of operating excitement in the coming week. Remember to look out for a disturbed Kp index value of 6 or greater.

The last part of the sporadic-E season is playing out this week taking us to the end of the month. These ‘last hurrahs’ are usually characterised by QSOs of very limited duration on the 10m band, or perhaps up to 6m, and mainly over the southern half of Europe.

This usually favours southern UK stations but, notwithstanding the previous comments, some years have seen isolated Sporadic-E events in the first part of September. But they are certainly not reliable.

Moon declination is positive but still rising, reaching maximum on Wednesday, so long Moon visibility windows and high peak elevations continue. We are past perigee now, so path losses are increasing again. 144MHz sky noise is low but increasing to a moderate 500 Kelvin on Wednesday before falling back to low at the end of the week.

Category: GB2RS Propagation News