Propagation News – 9 February 2025

Last week went pretty much as predicted. The solar wind from a large coronal hole impacted the Earth on Saturday 1 February, pushing the Kp index to four. The hole was so large that the geomagnetic disturbance lasted until the early evening on Sunday.

Once the solar wind speed had dropped, things got back to normal and the Kp index has been in the range of 1 to 2 ever since.

The event appeared to have had little effect on HF propagation, with maximum usable frequencies over a 3000km path remaining above 28MHz during the daylight hours. So it looks like we dodged a bullet.

At the time of writing, we have had 21 M-class flares in three days.

A solar flare measuring M8.8 was detected around active region 3981, peaking at 0358UTC on the 3 February. This was the strongest flare yet from this region in terms of peak X-Ray flux. However, the flare itself was impulsive and was not the source of a coronal mass ejection.

Over the next week, NOAA predicts that the solar flux index could fall slightly to be in the 180 to 200 range. Make the most of the good propagation as we may be entering a period of unsettled geomagnetic conditions again from the 10 to the 17 February. NOAA predicts that the Kp index could rise to a maximum of 5 on the 13 February but is likely to be in the range of 3 to 5 over the seven-day period.

Part of this may be down to another coronal hole which became Earth-facing on the 6 February. There is also a good chance that we could get an X-class eruptive flare from active regions 3981 or 3978, which could result in a coronal mass ejection.

We recommend you keep an eye on solarham.com for daily updates.

VHF and up

High pressure during the second half of last week brought some useful tropo conditions. As this week, ending today the 9 February, comes to a close there are some wintry showers along North Sea coasts, which may produce some snow and rain scatter. However, this may be weakened by the nearby high pressure.

By the end of this week, ending today the 9 February, there will be a change of weather pattern as the high, having now migrated to Scandinavia, leaves room for Atlantic weather systems to encroach from the west during the coming week. This could bring rain scatter possibilities to the western side of the country. These should be more useful than the eastern coast ones at the end of last week since the rain will probably be heavier and the fronts slow-moving.

This time of year is something of a desert for Sporadic-E propagation although look out for lesser events as a result of jet streams. You can track these on the Propquest website.

Keep a look out for auroras during the week beginning tomorrow, the 10 February. The likelihood of M-class flares is around 85%, while the chance of X-class flares is approximately 20%. So keep an eye on the Kp index for any potential solar events that could cause auroras.

Next week, there are no major meteor showers. The next significant meteor shower, the Lyrids, will become active in April. Keep checking the pre-dawn period for random meteors.

Moon declination reached a maximum yesterday, Saturday the 8 February. Path losses are still low but will increase throughout the coming week. This means that this weekend, ending today the 9 February, should produce good activity for EME, especially on the GHz bands with long Moon windows and high peak Moon elevation.

144MHz sky noise is moderate this weekend, ending today the 9 February, but falls to low for the rest of the coming week.

Category: GB2RS Propagation News