Propagation News – 19 May 2024

| May 17, 2024

After last weekend’s auroral spectacular it was nice to see the Sun calm down a little and the bands get back to normal. But that didn’t last long.

To recap, on Friday 10 May the Kp index shot up to 9, due to the effects of a number of coronal mass ejections, while the HF bands closed down in the subsequent geomagnetic storm.

While there were visible aurora across the UK and Europe, HF propagation really suffered and didn’t start to recover until the late afternoon on Saturday 11 May.

The main culprit, active region 3664, has now rotated out of view, but that doesn’t mean we are out of the woods just yet.

Solar flares can cause short-term disruption to HF propagation due to their X-rays penetrating deep into the D-region and causing signals to be absorbed. Subsequent coronal mass ejections can cause longer-term degradation of the F2 layer with reduced maximum usable frequencies, noisy bands and auroral conditions.

At the time of writing, the Kp index stood at 6 again so it looks like unsettled geomagnetic conditions are continuing with a moderate G2 geomagnetic storm in progress.

Low to moderate activity is now expected, with a slight chance of further strong-class flares. The regions currently on the visible disc are smaller and simpler, with isolated M-flares possible from these. However, a new active region, now rotating into view, has already emitted an X-class solar flare.

Next week, the United States Air Force predicts that the solar flux index may remain in the 160 to 180 range. HF conditions remain a lottery as they can be badly affected by solar flares and coronal mass ejections.

It is best to keep an eye on for updates, and also for near real-time reports of the critical and maximum usable frequencies.

VHF and up

The weather remains on the unsettled side of things with areas of rain and some thunderstorms over the country, especially the south as we end this week. As this report is being read out, high pressure is becoming established over northern and western Britain.

This may eventually take a tenuous hold over the rest of the country during the second half of the coming week and into next weekend, the 25 and 26 May.

This high pressure, although fairly weak, may help with some Tropo for those in northern Britain in the 144MHz May Contest and the Backpackers Contest this weekend, ending the 19 May. It may also be helpful to those taking part in the 1.3GHz UK Activity Contest on the 21 May. However, the conditions may not be of much use in the south as another low arrives from the continent.

Overall, rain scatter on the GHz bands will probably be worth exploring in the rainy areas again, since some of the showers may be heavy and thundery.

The prospects for aurora are still worth keeping in mind despite the recent stunning event. Minor non-visible events can still provide a reasonable radio aurora to explore.

The Sporadic-E season continues to develop. And with such unsettled weather, there are plentiful jet streams to act as source regions for turbulence, which can propagate up to the E region where they can generate Sporadic-E.

We are currently at the tail end of the Eta Aquariids meteor shower. A few meteors from this shower will continue to appear, but no major shower is expected this week.

The lowest Moon declination occurs this coming Friday. With the Moon being full on the 23 May, a clear sky should reveal an impressive ‘Flower Moon’.

For EME, path loss will still be relatively high, although the Moon is starting to move back towards its closest point to Earth, or perigee.

144MHz sky noise starts the week low but rises to high on Saturday the 25 May.

Category: GB2RS Propagation News