Propagation News – 30 May 2021

“May you live in interesting times.” So says the ancient Chinese curse, and last week was interesting, to say the least. Sunspot region 2824 was joined by region 2826, pushing the solar flux index to 88. At the same time, a coronal mass ejection from region 2824 threatened to push the Kp index high on the 25th. The reality was that the solar matter actually struck the Earth late on the 26th, elevating the Kp index to five.

The after-effects of the enhanced solar wind were still being felt on Thursday the 27th with the Kp index still fluctuating between three and four. The solar wind speed stayed above 400km per second affecting MUFs over a 3,000km path. On Thursday they were distinctly below 18MHz after an enhancement the evening before had pushed them to nearly 24MHz.

The good news is that Sporadic-E was much in evidence last week with numerous multi- and single-hop openings reported. VU2XO in India was worked from the UK on 10 metre SSB, as was YI1SAL in Iraq. An unusual copy was the German icebreaker Polarstern signing as DP0POL/MM on 28MHz WSPR.

The solar flux looks like it will diminish next week, according to NOAA, with the SFI in the mid-70s again. But at the time of writing, there were few signs of major coronal hole activity next week and NOAA predicts that the Kp index will hover around two.

So it looks like it could be another week where Sporadic-E propagation dominates HF activity with perhaps reduced F2-layer activity, but with more settled geomagnetic conditions.

VHF and up

At long last there are signs of some proper summer weather as high pressure returns. This will mean that Tropo should appear as a good VHF/UHF mode for much of the next week. Worth noting that paths can be limited during the daytime as heating breaks down any surface night-time inversion, so the operating rule is to concentrate on evenings and overnight for Tropo paths.

The Sporadic-E season is well under way but due to its sporadic nature it was no surprise that we failed to predict the short opening on 144MHz from the UK to Italy and the Balkans last Tuesday.

Late May and especially the first weeks of June usually produce something spectacular, but the jet stream positions look slightly less favourable in the coming week. Remember that optimum times for Sporadic-E are the mid-morning period and again late afternoon and early evening.

Toward the end of next week, the models suggest that we may see a showery breakdown with a possibility of thunderstorms. These are ideal sources of GHz band rain scatter from the large cumulonimbus clouds.

The Moon passed minimum declination yesterday, so visibility windows and peak Moon elevations will increase throughout the week. We also passed perigee last Wednesday so path losses will also increase.

No significant meteor showers this week so continue to be active around dawn for the best random meteors.

Category: GB2RS Propagation News