Propagation News – 16 April 2023

A news item this week suggested that the peak of solar cycle 25 could be coming earlier than expected. According to a paper in Frontiers in Astronomy and Space Sciences, by solar scientist Dr Scott Macintosh, solar maximum may now be coming between late 2023 and mid-2024. So, make the most of the higher Solar Flux Index now!

Solar activity picked up nicely over the past week. The solar flux index rose to 154 and there were eight active regions on the Sun’s visible face by Thursday 13 April. Nevertheless, daytime maximum usable frequencies, or MUFs, remain down a little, which has probably more to do with seasonal ionospheric changes than reduced sunspot activity.

As we head towards Summer we will see the daytime F2-layer MUF decline further before it picks up again in the Autumn.

We also saw some M- and C-class solar flare action this week, but this was not really enough to cause serious problems to the ionosphere.

Next week NOAA predicts the Solar Flux Index will continue to increase, perhaps peaking at 160 around the 16 to 18 April. Unsettled geomagnetic conditions are forecast for the 18 April, perhaps with the Kp index rising to four.

The forecast for International Marconi Day on the 22 April is for a Solar Flux Index of 155 and a declining Kp index of three, which bodes quite well for the event.

In all, the Solar Flux Index is expected to be in the range of 140 to 160 for the rest of the month.

VHF and up

A big contrast is coming next week, so it’s time to dust off the VHF gear again!

The unsettled weather of this last week will make a complete swap over to more settled high-pressure systems next week.

Initially, on Sunday this will appear as a ridge over the North Sea from a large high over Scandinavia. This will then gradually extend across the country and will eventually be joined by a second high west of Britain.

The end result will be enhanced Tropo prospects in the coming week and potentially good conditions for the 23cm UK Activity Contest on Tuesday the 18 April and the 4m UK Activity on Thursday the 20 April.

Those who enjoy rain scatter propagation in this current showery weather will have to look for other modes by Sunday, once the high pressure builds.

As we are coming out of the Winter lull in meteor shower activity, with the medium-rate Lyrids peaking on the 23 April at 0100UTC with a Zenithal Hourly Rate, or ZHR, in the 20s, it’s well worth a look for meteor scatter contacts.

The end of April normally prompts a return of isolated Sporadic-E reports on the 10m band and perhaps even with data modes on 6m. The upper troposphere jet stream charts suggest it’s got some potential, especially between Mediterranean countries although not quite so positive for paths nearer to home.

The solar conditions may continue to offer a random chance of some aurora, so remember to keep an eye on the Kp index if it goes above five.

For EME operators, Moon perigee is on Sunday so path losses are at their lowest. Moon declination is rising, going positive on Tuesday meaning increasing Moon time and increasing peak elevation passes.

144MHz sky noise is low, but the Moon is close to the Sun on Wednesday and Thursday meaning high Sun noise for those days.

Category: GB2RS Propagation News