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.
