Propagation News – 19 March 2023

| March 17, 2023

Last week was split in two, in terms of HF propagation. The first half of the week was characterised by excellent high-band conditions, with many people commenting on how good things were. The Kp index was low, there was a lack of solar flares and the solar flux index was high—perfect for HF.

There were reports of openings to Hawaii and Alaska on 10m, and Bob, MD0CCE said 10m had been open to the Pacific every night for the last five or six days.

But it didn’t last, and by Wednesday it all went pear-shaped.

The Earth was hit by a fast solar wind with a southward-pointing Bz on Wednesday, the 15th, which increased the Kp index to 5.67. Its impact on the ionosphere was quick and very damaging, to such an extent that the two ‘local’ digisondes at Fairford and Chilton couldn’t detect the F2 layer, leaving their traces blank.

It happened again on Wednesday evening, with the Kp index hitting 5.67 once again.

Luckily, it didn’t last long and the Kp index was back down to less than two by the morning and the MUF over 3,000km was back over 28MHz by mid-morning on Thursday.

Next week, NOAA predicts that the solar flux index will remain in the range of 135 to 145. Unsettled geomagnetic conditions are forecast for the 20th but, as we know, anything can happen at this point in the solar cycle. Look for a low Kp index but, above all, get on the bands and see what you can work!

VHF and up

The unsettled weather pattern seems likely to continue through the coming week driven by an undulating jet stream over the British Isles. This will mean, for yet another week, there is unlikely to be much good tropo. It’s not all bad news though, since the unsettled part of the weather story may introduce some rain scatter on the GHz bands.

The mention of jet streams should, in a month or so, raise the promise of some sporadic E activity, which is often geographically related to the position of jet streams. It’s probably a bit early for that, although it could be worth considering a look at 10 and 6m as we move towards the end of the month.

Ten metres, and 6m if you’re in the far south-west, can also give some good trans-equatorial propagation this time of year. This is typical of the changeover period from southern hemisphere to northern hemisphere sporadic E activity.

As usual, the chance of aurora is still around, so keep a watch out on the clusters or for all the latest news. Early morning random meteors should stay on the checklist too.

For EME operators, moon declination is low but rising, going positive again on Wednesday meaning Moon availability windows will lengthen. The Moon is at perigee today, so path losses are at a minimum. 144MHz sky noise is low this week, apart from the whole of Tuesday when the Sun and Moon are close to eclipse.

It is perhaps worth reminding new licensees that preparing a good list of HF and VHF beacons to monitor can be worthwhile, especially in quieter times before the summer sporadic E season gets under way.

Category: GB2RS Propagation News