The Sun remained spotless this week, other
than the hint of a new sunspot coming around its limb as this report was being
written.
The solar flux index reflected this, sitting around the high
60s, although it did reach 71 on Thursday morning. Geomagnetic conditions were
quiet at the beginning of the week, but a solar wind stream from a large solar
coronal hole was predicted to hit Earth later on Thursday, the 19th. This
normally means noisy HF bands, and depressed maximum usable frequencies (MUFs)
after a possible initial positive phase.
We are now seeing a shift
towards more summer-like ionospheric conditions in the northern hemisphere. At
this time there is a chemical change towards more diatomic molecules in the F2
layer and fewer monatomic species. The diatomic molecules are more difficult to
ionise and as a result MUFs can suffer.
Coupled with the lack of
sunspots, we are now seeing daytime MUFs struggling to get above 16-17 Megahertz
at times, despite the quiet geomagnetic conditions.
The upside is that
night-time MUFs are staying higher, with seven Megahertz possibly staying open
to DX over a 3,000km path through the night. A phenomenon that has been spotted
is that the MUF is sometimes rising again for a short period after sunset. It
might be worth checking 14MHz around 2000hrs UTC as this has showed itself a few
times on the ionosonde data.
Next week, NOAA predicts the solar flux
index will remain around 69 and geomagnetic conditions are predicted to be
quieter from Monday onwards after the weekend’s high K-indices.
These
settled conditions could bring better DX from Tuesday or Wednesday, once the
ionosphere has settled. As we’ll explain in the VHF section, you may still have
to wait a week or two before the start of the summer sporadic E
season.
VHF and up:
Last week ended with high pressure near
southern areas declining during the weekend as low pressure moved in from the
Atlantic towards northern areas.
There may be slightly enhanced tropo
conditions around at first but these could weaken as the low takes over. This
could introduce showery weather with a prospect for rain scatter on the
Gigahertz bands.
The 2018 sporadic E season is nearly here! It usually
starts with a few fleeting SSB and CW signals across southern Europe, possibly
not within range of UK stations, but with new digital modes, we might be lucky
this early.
Since the location of sporadic E geographically can be
influenced by the position of the jet stream, there may be some possibility of
paths from the UK to the south-east into the Balkans and east to the Baltic
states. The other possibility, based on expected jet stream positions, might be
from Spain down to the Canaries.
Anyway, before it all kicks off, it is
worth making that list of useful beacons on 10m or 6m so that you can quickly
find the openings—just Google “G3USF beacons”. Also, use propquest.co.uk to find
the daily jet stream positions.
Now we are in April, meteor activity is
picking up again. The first significant shower, the Lyrids, peaks Sunday, 22
April sometime between 1000 and 2100 UTC.
Moon declination is still
positive, but decreases all week, going negative—that is, south—this coming
Friday. Losses will also increase as the Moon heads out to apogee, its furthest
point from Earth. It’s another good week for EME then, with long windows and
high Moon elevations.
