Propagation News – 10 September 2017

Last week the Sun caught every one out. While NOAA predicted the solar flux index would be in the mid-70s, the sudden appearance of a large number of sunspots pushed it up to 183 on Tuesday, although it had calmed down to 122 by Wednesday. This had a major impact on the bands, with openings up to 10 metres being reported, though many or all of these may have been due to sporadic E. To be fair to NOAA, these spots were only just appearing around the edge of the Sun as last week’s report was being prepared.

Unfortunately, this new sunspot activity also resulted in numerous X-class solar flares, their associated coronal mass ejections and a proton storm. The K-index was pushed up to five on Tuesday and four on Wednesday and Thursday, impacting HF conditions adversely. Next week the larger spots will have rotated off the Sun’s visible surface, so the question is: what will follow them?

At the time of writing it looks like the Sun may calm down a little, although there is evidence of some new spots growing. NOAA predicts the solar flux index may decline into the 80s or 90s by the end of the week, with unsettled geomagnetic conditions from around the 13th to the 17th.

The good news is that each week we edge closer to better autumnal HF propagation, so expect higher maximum usable frequencies and better DX. October should be even better, so make sure your antennas are ready.

VHF and up

After last week’s class X9.3 solar flare, keep your beams to the north and look for any auroral propagation on six, four and two metres. The big sunspot group will have rotated off the Sun’s visible surface by now, but, as we said, it may not be the last one we see during this period.

The 2017 sporadic E season struggled into the first week of September, but we sense we must be near the end now. That leaves tropo as the next best option for some DX at VHF. Unfortunately, for much of the next week the UK weather pattern is dominated by low pressure, bringing unsettled and windy weather—so tropo also looks like a non-runner. Such changeable weather, often showery, may produce some rain scatter on the GHz bands, otherwise it’s thin pickings for weather-related propagation modes.

With only minor meteor showers this week, continue to look around dawn for the best random meteor scatter contacts.

We have positive Moon declination all this week. So, combined with low losses as we approach perigee on Wednesday, it’s a good week for EME with long morning and daytime Moon windows.

Category: GB2RS Propagation News