Propagation News – 25 June 2023

We had yet another week of high solar flux, plenty of sunspots, but also a major solar flare.

The solar flux index reached 180 on 20 June 2023 with a massive spread of sunspots across both solar hemispheres. But an X-class solar flare erupted on the same day. This was only just X-class though, as at X1.1 it barely hit the requirements. Luckily, its associated coronal mass ejection was directed away from Earth.

We passed the summer solstice this week so are now heading towards autumn. Don’t worry too much, though, as there is plenty of summer left, complete with its lower daytime maximum usable frequencies (MUF) and high levels of D-layer absorption. Fortunately, multi-hop sporadic E is also bringing occasional DX on the higher bands.

As we pointed out last week, night time MUFs remain high, partly due to seasonal norms and partly due to the high solar flux.

There were reports this week of 15m CW still being open at 03.30 local time, when Paul, MM0ZBH worked the VP6A DXpedition on Ducie Island. There have also been many reports of VP6A being worked on the 80m band at around 0800UTC.

Next week the Space Weather Prediction Centre puts the solar flux index at around 165 to 180 again. We can expect unsettled geomagnetic conditions once again around the 27th and 28th of this month.

Daytime F-layer MUFs over a 3,000km path are generally around 21MHz, but there are occasional surprises. Sporadic E still dominates on the 10m band. At night, MUFs over 3,000km are often around 14 to 18MHz, again with some surprises at times.

VHF and up

After a slow change to a more summer-like pattern of showers and sunshine with occasional fronts in the last week, it does seem like it’s a continuation for the coming week.

This means further opportunity for rain scatter on the GHz bands and with a reasonable chance of tracking the storms with any of the online weather radars.

There will be a tendency for higher pressure close to southern Britain with possible tropo, which will extend south across Biscay to northern Spain or farther south towards the Canaries and perhaps beyond. It may even offer paths east across the southern North Sea towards Denmark.

There have been some reasonable sporadic E paths within Europe and beyond to the Americas. Paths have also opened eastwards to the Far East or Middle East and there is no reason not to expect similar for the coming week.

As next week progresses, the jet stream distribution may favour paths to Scandinavia and the Baltic, plus across the Atlantic to the States.

The recent unsettled solar conditions may affect the prospects for sporadic E propagation if the Kp index becomes too high, but on the plus side it could then be worth checking for aurora. Don’t forget that random meteors can provide a few chance QSOs using meteor scatter propagation and there have been audible meteor ‘pings’ on some sporadic E QSOs recently, so they do exist!

Moon declination goes negative again on Monday—so shortening Moon windows. Path losses will fall all week, and 144MHz sky noise is low to moderate until next weekend when it reaches more than 2500 Kelvin on Sunday.

Category: GB2RS Propagation News