Propagation News – 28 August 2016

This week was a mixed bag in terms of the sun and HF propagation. The solar flux index hovered around the 80 mark, but there was a geomagnetic disturbance on Tuesday evening that sent the K-index up to five for more than six hours. This prompted warnings that aurora might be visible from lower than usual latitudes.

There are signs that the summer HF doldrums are starting to wane a little. The daytime critical frequency, as measured by the Chilton Digisonde near Harwell, peaked at more than 6MHz on Tuesday afternoon, bringing some signs of life on 15 metres. This continued to increase during the early evening, but was probably due to the early positive phase of the subsequent geomagnetic and ionospheric disturbance caused by plasma from a coronal hole. It does go to show that you never quite know how HF propagation may pan out, so it is worth keeping an eye on the K-index at solarham.com.

Next week NOAA predicts the SFI will be in the range 75-85. Ongoing coronal activity and associated high speed solar wind streams will push the K-index up to five midweek, with the unsettled conditions predicted to last across the weekend, potentially causing problems for HF SSB field day.

VHF and up propagation

There were some good tropospheric openings around last week. As we head into the weekend there will be a ridge of high pressure close to southern Britain, which in some models remains close by for much of the coming week.

This could give some extended tropo paths to the south across Biscay to northern Spain and the Azores as well as across the North Sea to Denmark and north Germany. Scotland will be slightly more breezy at times with rain or showers, so is not quite as likely to see the tropo conditions.

It really is getting close to the end of the main sporadic E season and, since the jet stream pattern is looking weak and not well placed for paths into Europe, we may have little to get excited about.

The new moon on the first of September, together with decreasing moon declination, means an increase in degradation on EME paths.

With the Perseids meteor shower now a passing event, the Alpha Aurigids may produce some sporadic activity between 29 August and 3 September. This is a class II shower and comprises Halley’s comet debris. The Orionids shower is spread over many months between late August and mid-November, but early activity may be detected this coming week.

Category: GB2RS Propagation News