Propagation News – 18 February 2024

We had an interesting week with the threat of a major coronal mass ejection at any time with so much sunspot activity. In the end, it pretty much amounted to nothing, with the highest Kp index only reaching 4.33 on 11 February.

That’s not to say we didn’t have solar activity. Far from it, as the solar flux index reached 208 on the 12 February  and has been consistently above 180 all week. We also had high proton levels as the positively charged particles streamed past Earth. This was the result of an eruption early on Monday morning from beyond the southwest limb. This may have affected HF signals going over the poles.

Otherwise, we had numerous low-level solar flares to contend with, but none of them were stronger than M-class and so of little consequence.

So where did this leave us in terms of HF propagation? All in all, not bad with maximum usable frequencies, or MUFs for short, over 3,000km consistently above 28MHz in daylight hours. In fact, daytime MUFs were peaking above 33MHz according to the Dourbes ionosonde.

Looking further ahead, we are now heading towards the equinox period, so we can expect MUFs to fall from their winter highs. The good news is that we can expect north-south paths to improve. The equinox is traditionally a better time for auroral conditions.

If you want to work the USA on 28MHz you still have a couple of months left to do so, but expect transatlantic propagation conditions to decline by the time April arrives. The good news is that propagation to South Africa, South America and the Caribbean may improve.

Next week, NOAA predicts that the solar flux index may reduce and be in the range 155 to 165. Geomagnetic conditions are predicted to be quiet but, as always, keep an eye on solarham.net for a near real-time update as the risk of a coronal mass ejection, or CME, remains high. To recap, an Earth-facing CME could increase the Kp index, reduce MUFs and generally give poor HF propagation for up to a day or so.

 VHF and up

The basic weather pattern remains unsettled with a series of frontal systems crossing the country during the period. This leaves little room for any Tropo other than the occasional transient ridge of high pressure between successive weather systems. It does however give plenty of scope for rain-scatter enthusiasts to try their luck on the GHz bands.

The solar conditions continue to give hope for an increased geomagnetic Kp index, which would be a good signal for potential aurora if it goes above 5 as evidenced in visual displays over northern Britain last Tuesday night, the 13 and 14 February.

As usual, the other propagation modes can still surprise us, even though this is not strictly the best time of year. The large number of satellites in operation means that QSOs can be guaranteed even with simple hand-held equipment. So, have a look at the AMSAT-UK pages and the RSGB website for details and give it a go!

Also, a reminder that the best time for random meteor scatter QSOs is around dawn, and that the high solar flux could see some 50MHz openings if the Kp index remains low, especially for the far South and West of the UK.

For EME operators, the moon reaches peak declination today, Sunday 18 February, so activity should be higher with high peak moon elevations and long moon windows. Path losses are moderate but rising and 144MHz sky noise is moderate, but falling after Monday.

Category: GB2RS Propagation News