Propagation News – 24 April 2016

It has been week of mixed HF propagation, good at times and lousy at others. The solar flux index declined from 102 on Sunday to 83 on Thursday, as only one lonely little sunspot remained visible.

The K-index, which is the three-hourly measure of geomagnetic disturbance due to incoming plasma from the Sun, has also risen and fallen, starting off at four last Sunday, and declining to one at times during the week.

Looking ahead, the solar flux index is predicted to be between 85-98, according to the US Air Force, rising as sunspot 2533 comes into play over the next few days.

It is bad news on the geomagnetic disturbance front. The Solar Dynamics Observatory’s extreme ultraviolet image showed a massive coronal hole looking straight at us on Thursday. The associated high-speed solar wind stream from this may hit the earth on Saturday, just in time for International Marconi Day. NOAA predicts the K-index could rise to four in the early hours of Saturday morning, tailing off to two by late afternoon. This may not bode well for HF propagation.

Unsettled conditions are expected to continue until 26 April with isolated active periods likely. Mostly quiet conditions are expected from 27 to 28 April.

VHF and up propagation news

After some high pressure during last week produced a little bit of tropo for stations in the North of England, we are returning to low pressure over the North Sea. This may eventually drift across southern England later in the week. The result is a return of a cool northerly wind and means that April showers will continue to be a theme this week, and hence give options for rain scatter on the gigahertz bands.

Last week, sporadic-E was reported on 10 metres and 6 metres and, with the continued presence of a jet stream blowing down across the UK into southern Europe, there is plenty of scope for further sporadic-E events this coming week.

The 2016 Lyrids meteor shower has passed its peak so it is back to random meteor scatter contacts in the early mornings.

Over the next few years, the Moon is entering a phase when high declination is combined with the moon being at perigee or closest to the earth. This means long, high-elevation moon windows will occur when path loss is at its lowest, improving EME conditions. This week, lowest declination occurs on Wednesday so expect short Moon passes in the early hours of the morning.

Category: GB2RS Propagation News