RSGB
GB2RS News Team
February 21, 2025
It seems we were a little over-ambitious in suggesting that last week would be better for HF propagation. It looked like we would avoid coronal mass ejections and see the Kp index fall to lower levels.
Unfortunately, the Sun had other ideas and a fast-moving solar stream, often moving faster than 500 km/s, had a south-pointing Bz, which coupled more easily with Earth and sent the Kp index up to four or more.
So even by Wednesday 19 February the Kp index was hitting five.
But it seems that the geomagnetic disturbance merely lowered the MUF from around 40-45MHz to 31-32MHz, so it barely affected HF propagation.
At the time of writing there had only been one M-class solar flare in the past five days, but more than 50 minor C-class events. There were no Earth-directed CMEs.
Nevertheless, there was DX to be had with the standout stations being the V73WW DXpedition to Majuro Atoll on the Marshall Islands, TI1RRC Costa Rica, and 5N9DTG in Nigeria. Upcoming DX next week includes OX3LX (Greenland), Dave G4BUO as 5W0UO (Samoa), TO3Z (Guadeloupe), 4S7SPG (Sri
Lanka) and FS/VA3QSL (St Martin).
Next week, NOAA predicts that the week commencing the 23 February could see the solar flux index starting at 170, but then rising to 195-200 as the week progresses. Geomagnetic conditions are predicted to start quietly, with a Kp index of two, but then become unsettled by the 27 to
29 February, with a maximum predicted Kp index of five.
If this scenario does pan out then we may expect the best HF conditions to occur at the beginning of next week, from the 23 to 26 February.
As always, keep an eye on solarham.com for day-to-day solar news, and perhaps monitor PSKreporter, the Reverse Beacon Network and DX Clusters for digital, CW and SSB HF propagation updates.
VHF and up :
The current spell of unsettled weather seems likely to continue through to the end of next week. There will also be significant windy weather at times. It is therefore not a particularly good period for Tropo, or big antennas for that matter.
This leaves us with rain scatter on the GHz bands and some of these scattering regions will be large areas affecting the whole of the country as active weather fronts pass by, rather than more isolated and harder-to-follow showers which often provide our rain scatter.
Meteor scatter is still within its quieter period with no major showers and better chances coming from random meteor activity, which tends to peak in the hours before dawn.
Recent solar activity has provided some weak auroral conditions on many days. As usual, check for high values of the Kp index as a good indicator, or even listen for a watery tone on the LF bands. Ultimately you will need to see the Kp index going to at least five to make it worth checking for auroral signals on VHF.
We are still in the dormant period for Sporadic-E propagation, which is a shame in view of the powerful jet streams likely during this stormy weather. These would produce good Es prospects in the main summer season, but weaker Es at low VHF are still a possibility despite being out of season.
Moon declination is at minimum today, Sunday 23 February, and path losses are decreasing as the Moon moves closer to Earth as it heads to perigee on Saturday 1 March. 144MHz sky noise goes high this weekend, beginning Saturday 22 February.
https://rsgb.org/main/blog/news/gb2rs/propagation-news/2025/02/21/propagation-news-23-february-2025/
(Mike Terry, UK/BDXC)
