Propagation News – 16 February 2025

Two large coronal holes on the Sun’s surface have been spraying solar material towards Earth, pushing the Kp index to a high of 4.67.

The solar wind speed has been consistently higher than 500 kilometres per second and, with a south-pointing interplanetary magnetic field, the plasma has flooded into Earth’s magnetic field. There have been a few aurora warnings, but these have only been minor.

As a result, the ionosphere has not been too badly affected and daytime maximum usable frequencies over a 3,000km path have generally remained above 28MHz, with the odd dip towards 24MHz.

Coronal mass ejections have not made an appearance and there were only three M-class flares between the 9 and 13 February.

Meanwhile, the solar flux index fell to the 150s and 160s last week.

Recent HF DX has included the V73WW DXpedition on the Marshall Islands, which has been worked from the UK, including on the 40, 30 and 20m bands using CW. The TX7N DXpedition to Marquesas Island in French Polynesia has just finished. It wasn’t an easy path, but it was worked from the UK on all bands from 30 to 12m using FT8, CW and SSB.

Next week, NOAA predicts that the solar flux index could rise a little, to be in the 180 to 190 range. Once Earth is free from the effects of the current coronal hole stream, we may expect the Kp index to retreat, perhaps to a maximum of 2.

So, DX next week could be quite reasonable but, as always, keep an eye on solarham.com for daily updates.

VHF and up

The lingering high pressure just to the east of the UK is holding weather fronts over western Britain for the time being with any tropo benefits confined to eastern areas, and being marginal at best.

During the coming week, changes will be slow but gradually a more determined push on the Atlantic fronts may bring them over most areas, except the extreme southeast of the country.

This will make rain scatter more accessible although the models suggest that the fronts are likely to become weaker. So, they will not be especially useful by the time they reach the southeast. Sporadic-E is in its quiet season now, as are the meteor scatter prospects, with no major showers in attendance until the spring Lyrids in late April.

Perhaps this quieter time is a chance to do some operating housekeeping. For example, you could update a list of nearby repeaters and beacons to help you track developing openings. Or maybe you could consider trying a new mode or band. Perhaps you could learn to use digital modes for meteor scatter. Maybe consider joining the increasing numbers trying CW on the 2m band.

Moon declination went negative again on Saturday 15 February and path losses are rising as the Moon moves away to apogee, its furthest point from Earth, on Tuesday the 18 February. 144MHz sky noise is low for most of the coming week but goes high for the weekend of Saturday the 22 February.

Category: GB2RS Propagation News