Propagation News – 14 April 2019

This has been a difficult time for HF. The solar wind has remained active and the Bz component exhibited several periods of prolonged southward deflection, meaning it more easily coupled with the Earth’s magnetic field. Solar wind speed ranged mostly from 425-475km per second and this was enough to keep the Kp index elevated, often to four. The net result was that conditions were pretty rotten, with even 14MHz struggling to open at times. However, the solar flux did increase to 78 thanks to the return of sunspot number 2738. This is large, but appears to be only producing very minor B-Class flares. An isolated C-Flare may also be possible.

Next week should be more settled, geomagnetically, with a maximum Kp index of two and solar flux of 74. If the solar wind drops we may expect fair HF conditions next week.

This current solar cycle had a peak average of 82 sunspots. The Solar Cycle 25 Prediction Panel experts have just said the next may have a slow start, but is anticipated to peak with solar maximum occurring between 2023 and 2026, and a sunspot range of 95 to 130. This is well below the average number of sunspots, which typically ranges from 140 to 220 sunspots per solar cycle.

VHF and up

It seems that high pressure remains firmly in control to the north of Britain and over Scandinavia for much of the coming week. This would normally mean that tropo should get a mention, certainly for eastern areas, but the air mass is fairly dry and therefore not ideal for producing the required change in refractive index needed for tropo.

In the south and west there will be some spells of rain and a possibility of some rain scatter, but it will also be rather windy at times. There should be a trend later next week for a more moist and warmer flow to cross the North Sea and this could introduce extensive misty low cloud along the east coast. This is exactly what’s needed for better tropo prospects in eastern areas.

We are rapidly approaching the sporadic E season and should start to see some paths on 10m and possibly 6m opening up within Europe. It is worth checking the clusters and beacons for band activity. Digital modes like FT8 will benefit first, but it is possible that SSB and CW will start to show in the second half of the month. The typical early paths are often out to the eastern Mediterranean and over the Pyrenees, usually just out of reach from the UK, but a good sign should they occur.

Although the Lyrids meteor shower does not peak until next week, the first indications of the shower will begin to be noticed around 16 April, probably with a gradual increase in the number of meteors encountered growing during the forthcoming week. Don’t expect great things this week, but do keep an eye on the ON4KST chat for reports of meteor bursts. Better still, keep listening on one of the more distant 6m, 4m or 2m beacons for the occasional ping.

As the moon declination decreases during the week, 144MHz moon background sky noise gradually increases. However, path degradation is low due to the Moon’s closest approach, or perigee, on the 17th. Libration is also low on the 17th and this will help 1296MHz EME, as CW characters will be less ‘chopped’. The 17th would be good day to try EME.

Category: GB2RS Propagation News