Propagation News – 17 April 2022

| April 14, 2022

We had a week with declining solar flux index numbers, but with the ever-present threat of coronal mass ejections. The SFI declined from 101 on Sunday to 96 on Wednesday with the possibility of further falls as the week goes on. A solar filament located near the centre disk of the Sun erupted early Monday morning generating a faint, halo coronal mass ejection (CME) that appeared to be squarely Earth directed.

A moderate (G2) geomagnetic storm watch was added for the 14th and sky watchers at middle to high latitudes were also put on alert for aurora.

Meanwhile, the quieter geomagnetic conditions earlier in the week saw 10 metres open up to some good DX. Laurie, G3UML reports a long path opening to Australia on 20m CW from 0730 to 0800UTC. He worked two VK2s and a VK3, and listened to VK5QD who was very loud.

Next week NOAA predicts that the SFI may climb again, perhaps into the range 100 to 110.

Geomagnetic conditions are predicted to be generally quiet, but with the ever-present risk of CMEs pushing the Kp index up to perhaps four or five at times. A pair of coronal holes became Earth facing on Thursday as well, which may bring unsettled conditions again this weekend. If the Kp index stays low we can expect MUFs to be near seasonal norms, perhaps with openings up to 21 and even 28MHz at times.

Look out for occasional early-season Sporadic-E openings as well, which could bring short-skip openings into Europe on 10 metres.

VHF and up

The high pressure over the North Sea and Scandinavia will decline slowly allowing a new area of low pressure over the nearby Atlantic to drift east into southern Britain during the Easter weekend. This will mean that any Tropo benefits, particularly over the Irish Sea and North Sea will decline during the weekend.

The new low will bring areas of showery rain across the country with a chance of rain scatter propagation. This is likely to be a pattern for much of the following week with low pressure over southern areas and occasionally expanding bands of rain farther north.

The solar activity has continued to provide aurora options, so again worthwhile checking the clusters and Kp index for early signs of auroral activity. It is also a given that random meteor scatter is always available, especially for those who like to be up early in the morning!

The main mode to keep a watch out for during the coming week is Sporadic-E, which is just beginning to make an appearance on 10m and even higher bands using digital modes.

Jet streams are important as potential sources of the atmospheric gravity waves that can contribute to Es. You should look to the jet stream 300hectopascal or hPa upper air charts to see where they are located. Try paths that cross them, especially where they cross mountain ranges like the Alps or Pyrenees. Note a hectopascal equals a millibar.

The website has a set of four 300hPa charts for the current day and from the beginning of May will also contain a daily blog highlighting that day’s prospects.

The Winter minimum of meteor show activity is coming to an end. This week the small daytime April Piscids shower starts on the 20th, and peaks two days later at 2200UTC. This also coincides with the peak of the larger, and currently active Lyrids shower also on the 22nd but earlier at 1300 UTC. With a ZHR of around 18 it should produce some good reflections.

Moon perigee is on Tuesday so path losses are at their lowest. Moon declination is negative again and reaches minimum on Thursday so Moon windows will be short and peak Moon elevation low. 144MHz sky noise is high, peaking at over 3000K on Thursday so combined with the low elevations a poor week for especially VHF EME.

Category: GB2RS Propagation News