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Propagation News – 7 February 2021

Last week was dominated by unsettled geomagnetic conditions. These were due to the effects of a high-speed stream from a solar coronal hole. The stream resulted in a co-rotating interaction region, or CIR. CIRs are transition zones between slow- and fast-moving streams of solar wind. Solar wind plasma piles up in these regions, creating density gradients and shock waves that can affect Earth’s magnetic field much like a coronal mass ejection, or CME. The net result was a Kp index that hit four with widespread visible aurora in the early hours of February 2nd. Unsettled geomagnetic conditions continued until at least Thursday with the Kp index eventually settling back to two.

Propagation wise, Tuesday morning saw 10 metres alive with FT8 signals. There was short-skip to Scotland, Wales and Ireland as well as longer paths to Croatia and the Canary Islands. Wednesday saw 4X4DX in Israel coming through. Chris, G0DWV managed to work Namibia and South Africa on 10 metres from his well-equipped station. He then moved to 12 metres and bagged the Dominican Republic, Paraguay, Venezuela, Ecuador and numerous North American stations. And all this with virtually no sunspots!

Next week NOAA predicts the solar flux index will be in the range 72-76. But a high-speed stream from another solar coronal hole may impact the Earth this weekend, sending the Kp index up to four. It will be interesting to see if we have an enhancement to the upper HF bands again. Keep an eye on 10 and 12 metres and also for a rapid rise in the real-time solar wind speed at solarham.com

VHF and up:

A disturbed end to this week with rain and snow giving us plenty to do without worrying about band conditions. There’s always GHz bands snow and rain scatter to try if you have the equipment. 10GHz rainscatter QSOs can be made over short ranges using high elevation, so put that tripod out in the back yard, chuck something waterproof over the equipment and make a sked!

On the Tropo front, there’s a hint of a temporary weak ridge down the spine of the country at the start of next week, and it may produce some sharp nocturnal temperature inversions over snow cover to bring up the odd distant repeater. Thereafter another low moves up the Channel with rain and snow for the south, while wintry showers affect northern areas. Later in the week a more vigorous Atlantic low pushes active fronts across the whole country. For VHF/UHF propagation this is not a good period, apart from some scattering on the GHz bands. February is the minimum month for Sporadic-E.

The Moon is at minimum declination on Monday, so visibility windows are at their shortest and peak Moon elevations are minimum. Perigee was last week so path losses are still low. 144MHz sky noise is high, over 2000K on Monday. On Thursday afternoon the Sun and Moon are within a few degrees of each other so Sun noise will dominate.

The Alpha Centaurids meteor shower peaks tomorrow, Monday, but with a zenithal hourly rate of just six, you’ll only see a slight enhancement on meteor scatter conditions.

And that’s all from the propagation team this week. (rsgb.org)

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