Propagation News – 30 March 2025

Last week’s space weather was dominated by a large coronal hole on the Sun. This was probably one of the largest we have seen for many years.

Moderate, G2, geomagnetic storming was observed following the arrival of a solar wind stream from the hole, with the wind speed exceeding 600 km/s on Wednesday 26 March. This pushed the Kp index to 6.33, depressing the MUF slightly.

Luckily, the daytime MUF over a 3,000km path mostly stayed above 28MHz, but it was slow to rise on Thursday the 27 March, when it took until 0900UTC to reach 28MHz. At the time of writing, the solar wind speed was in excess of 800km/s, so we can expect more disruption until at least Saturday 29 March.

Meanwhile, the solar flux index declined to 152 by Thursday 27 March, with only four small sunspot regions visible.

CDXC members have been discussing working New Zealand in the morning at the ZL sunset, often on low power. Listen and look for ZL4OL and ZL2CC, usually on FT8, but if conditions allow CW and SSB. 20m or 40m seem to be the favourite, and the VarAC data mode seems popular in ZL as well.

Next week, NOAA predicts the solar flux index will climb again, perhaps to 180 by the 4 April. However, unsettled geomagnetic conditions are forecast again, beginning on the 3 April. We may expect the Kp index to reach six, which could be the start of at least ten days of disruption.

VHF and up

The overall picture for the weather patterns in the coming week is that of high pressure, which means that Tropo should be available as a good mode for VHF bands.

There can be quite strong temperature inversions in the region of large well-developed areas of high pressure. The best performance will usually be around the edges of the high where the height of the inversion and ducting layer is typically between 0.5km and 2km above the ground, and can cover large distances for excellent DX prospects.

Occasionally, a shallow ducting layer can form near the ground overnight but often disperses by mid-morning. If you are in a good inversion region, try SSB or CW on the VHF/UHF bands, as paths of up to 1,500km can often be achieved from a good ‘tropo lift’.

The reverse side of the high-pressure systems is that we will have low pressure nearby, mainly to the north and west of the UK. Any potential for rain scatter will mainly be over northwestern Britain, although an active front that was moving south on Friday 28 March was a good candidate for chance rain scatter on the GHz bands.

The prospects for meteor scatter are still largely dependent upon random meteors, which are usually best in the hours before dawn. Current solar activity will continue to trigger auroral alerts in the coming week.

Now onto Sporadic-E, and last week we had a few out-of-season isolated foEs ‘blips’ to between 5-7MHz, which was enough to produce propagation on 10m and 6m, albeit very fleetingly.

There have already been some equinox-related 6m trans-equatorial propagation or TEP workable from the Southern part of the country, so keep an eye open late morning for Africa and late afternoon for South America.

EME path losses have continued to improve until perigee this morning, the 30 March. Moon declination is still falling, and reached a minimum last Friday, the 28 March. Moon windows will increase throughout the coming week. 144MHz sky noise is low, apart from Saturday 29 March when the Sun was close to the Moon in the sky, rising to moderate next Thursday before dropping back to low for the weekend.

Category: GB2RS Propagation News