Propagation News – 1 September 2019
The past week was characterised by a low solar flux index and relatively-calm geomagnetic conditions. There were reports of numerous sporadic E openings this week that livened up the 10m band. On Thursday these spread from Serbia through to Germany, Finland and Norway and were probably caused by a strong jet stream, which can be seen on the Met Office 300millibar charts.
The Space Weather Services Bureau of Meteorology in Australia has been reporting that its T index, which can be best thought of as an “equivalent sunspot number”, has been hovering around zero after weeks of being very negative. This suggests that maximum usable frequencies may be up to 20 percent better than we have been experiencing, partly due to quieter geomagnetic conditions, and partly due to the seasonal change. Nevertheless, the Chilton ionosonde has been recording daytime F2 critical frequencies of about 4.3 to 4.7MHz, giving a maximum usable frequency over a 3,000km path of between 14 and 18MHz.
Next week NOAA predicts a solar flux index of 67, but a large T-shaped coronal hole on the Sun threatens to push the K-index up to six late on Saturday, the 31st, or Sunday, the 1st, as solar matter hits the Earth’s magnetic field. This may result in depressed HF conditions after an initial enhancement. These should settle by Tuesday or Wednesday, leaving the rest of the week with a K-index of two or three, and potentially better conditions.
VHF and up
The last week brought some welcome late season sporadic E to many parts of the UK, even reaching 2m on one occasion. This was an unusually-widespread opening geographically, with most areas from Scandinavia round to Portugal being worked. Sporadic E is possible into early September, so be sure to check the various blogs and clusters for activity. You haven’t got much time left to bag those missing squares!
The coming week will see unsettled weather generally with some showers or spells of rain, especially in the north. This may give a few opportunities for rain scatter. The south will be closer to high pressure over the continent and has the best chance of tapping into some tropo conditions, although it’s not really a strong option until near the end of the week, when high pressure builds in from the Atlantic.
The Moon is past perigee and declination goes negative again tonight, reaching minimum a week today. The EME week will be characterised by shortening Moon windows and rising path losses. There are no major meteor showers this week so stick with the usual pre-dawn enhancement for the best meteor scatter conditions.
Category: GB2RS Propagation News
