venerdì 22 luglio 2022

Propagation News – 24 July 2022

Last week was almost a repeat performance of the previous week. We had very disturbed geomagnetic conditions on Tuesday, with the Kp index hitting five. But then other days, like Wednesday, when conditions were much more settled. The solar flux index declined from its high of 176 last Saturday to 133 on Thursday. The Sun’s surface is still peppered with spots, but they are all fairly small and innocuous.

Nevertheless, there have been numerous C-class flares happening on a daily basis and two M-class flares last Saturday.

The popular press have been running their usual horror stories about CMEs hitting the Earth, threatening all sorts of doom and gloom. But to be honest, for radio amateurs it’s business as usual.

Sporadic-E had been most prolific earlier in the week with some relatively short-skip signals being stable over long periods. The ED4YAK beacon in Spain on 28.251MHz has often been audible for hours on end.

Next week NOAA predicts that the SFI will remain in the mid 130s, but predicts that geomagnetic conditions may be unstable over the weekend, before settling on Tuesday. If this is the case we can expect reduced MUFs over the weekend and a general lacklustre feel to HF, until the Kp index reduces again.

Make the most of the Es season while it lasts, as we may have seen the best of it, and we can’t expect an upturn in F2-layer propagation until mid to late September.

VHF and up:

It looks like a bit of a propagation mode mixture this coming week with something for everyone. It begins with a continuation of the typical summer warmth rather than the extreme conditions last week. Over northern areas, where low pressure remains close-by, we’ll see a few showers that might bring GHz band rainscatter opportunities. There will be a few showers in the south too, but also with a period of the Azores high building a ridge across southern Britain. This could bring some occasional Tropo throughout the week to southern areas, interspersed with isolated rain scatter opportunities in any showery interludes.

The Sporadic-E season continues apace with a bit of an uptick again last week, bringing some strong signals from south-eastern Europe. Summer jet streams are often rather scarce in more southern latitudes, but can occur fairly frequently over the UK and northern Europe. That will probably be the case in the coming week and suggests that paths towards Scandinavia, the Baltic states and eastern Europe will do best.

With four minor showers peaking around the 28th to the 30th, meteor scatter is worth trying, particularly around dawn, as will aurora propagation modes in view of the current unsettled solar activity.

The Moon is at maximum positive declination on Tuesday and also at apogee, its furthest point from Earth, so Moon windows are long and path losses are at their highest. 144MHz sky noise is low to moderate all week, but Thursday sees the Sun and Moon close in the sky, making EME very difficult due to sun noise in the antenna beamwidth. (