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.