This past week had been reasonably
settled, geomagnetically, with the K-index generally being between zero and
three at the beginning of the week. The noon-time critical frequency as measured
by the Chilton ionosonde near Harwell on Tuesday was just over 6MHz, which meant
40m often struggled for contacts close in around the UK, but 15 metres was
potentially open to DX at times. The critical frequency climbed higher during
Tuesday afternoon, which meant that 12 metres may have been open. This also
confirms that noon doesn’t always bring the highest critical frequencies.
We then had a succession of B-class solar flares on Wednesday. A large
recurrent coronal hole moved across the Earth-facing side of the sun and became
geo-effective from December 7th.
Enhanced geomagnetic activity,
including minor (G1) storm conditions then occurred on Thursday when a
high-speed solar wind stream passed Earth. Don’t forget you can get a short
pre-event enhancement just as the plasma hits and the K-index rises, but the
prognosis for HF is then not good if we get prolonged storming.
NOAA
predicts that the coronal hole effects will diminish after the weekend, leaving
a more settled ionosphere for the rest of the week. Conditions may become more
unsettled again from around December the 19th.
So Monday to Saturday
next week may be the best times for working DX on the HF bands, but don’t forget
to check the low bands for DX during late afternoon and through the hours of
darkness as we are at an optimum time as we near the Winter solstice.
VHF and up propagation news:
This week sees one of the biggest
meteor showers of the year. The peak of the Geminids is expected on Wednesday
morning at around 0020UTC, with a zenithal hourly rate of around 120. All the
low VHF bands will be affected, with EME-capable stations on 70cm also able to
make meteor scatter QSOs.
There seems to be a common theme in the
weather models for the coming week, which is that there is likely to be high
pressure nearby to the south and east of Britain, over the continent. A series
of low pressure systems will continue to pass by the north-west of the country
with cloud, rain and periods of stronger winds. This means that any tropo
conditions are likely to be confined to the southern and eastern half of
Britain, closer to the high pressure over the continent, which is the direction
to look for any tropo DX during the next week.
The latter part of the
week will probably see a stronger development of high pressure over the south of
Britain, maintaining the tropo options into the following weekend.
Low
losses and high declination this week make it a good one for EME contacts. E44QX
should be QRV on the GHz bands from Jericho until Wednesday.
