Propagation News – 18 April 2021

| April 16, 2021

The Sun continued to remain quiet last week with a maximum solar flux index of 75.3 on the twelfth and a maximum sunspot number of 17. Sunspot region 2814, whose physical width was equivalent to four Earth diameters, spawned a few B-class solar flares, but showed little sign of growing and as you read or hear this report will be rotating out of view on the Sun’s limb.

The STEREO Ahead spacecraft is showing some future potential spots, with two areas exhibiting magnetic activity, but it is too early to say whether these will amount to actual spots when they rotate onto the visible solar disk.

What is more obvious is a large coronal hole that will be Earth-facing by Friday and promising a high-speed solar wind that will hit us by late Saturday or Sunday. This is predicted to make the Kp index rise to an estimated five, although, rather like the rise in the Kp Index on Thursday the 15th, it will likely be short lived. As the Kp Index rises expect a decrease in maximum usable frequencies until the ionosphere recovers.

NOAA predicts the SFI will be in the range 72-75 next week with relatively calm geomagnetic conditions once we get past the Kp increase this weekend.

We are now probably just a couple of weeks away from the start of the Sporadic-E season, and as the weather forecast for this next week is quite good, it may be an ideal opportunity to check your 10m antennas.

One upcoming highlight is International Marconi Day on Saturday the 24th of April, when special event stations in locations with a significance to Marconi’s work will operate around the world. For more details, just search online for GB4IMD.

VHF and up

With another week of high pressure on the charts, it will be a Tropo theme for propagation. Although, for some of the time the surface air, which ideally should be cool and moist, looks likely to be cold and dry, so Tropo may not be as strong as it could be. Sometimes the presence of misty low cloud or fog in the morning will put things right temporarily, but conditions will fade thereafter as the fog or cloud clears.

Northwestern parts of the British Isles will have some spells of frontal rain and a chance of some rain scatter, but even here the high will become more dominant later. That leaves us with the approaching Sporadic-E season to consider. It’s coming, but these early season opportunities tend to be fleeting and more likely on the lower bands like 10m and 6m using digital modes.

With the Moon at maximum positive declination today and falling path losses, towards perigee a week on Monday, it’s a good week for EME. There will be long Moon windows and high peak elevations.

Thursday the 22nd sees the peak of the April Lyrids meteor shower, and on Friday the smaller Pi-Puppids. These showers signal the end of the annual meteor activity minimum and already there are signs of more meteor reflections being reported, so get looking at the usual frequencies for the mainly digimode activity.

Category: GB2RS Propagation News