Propagation News – 13 August 2023
Sunspot activity continues as we head towards solar maximum. Or have we already gone past that point? Identifying solar maximum can only really be done in retrospect. That is, after we have already had it!
Solar maximum is now forecast for early to mid-2025 so we still have some way to go.
Last week the Solar Flux Index declined from 176 on the 5th, to 153 on the 10th.
Geomagnetic conditions were mainly settled, other than a Kp index of 6.67 on the 5th. This was due to an incoming plasma cloud from a coronal mass ejection, or CME, that left the Sun on the 2 August.
We had not one, but two X-class flare events recently. These occurred on the 5th and the 7th. The event on the 5th was long in duration with a peak flux at 2221UTC. Luckily it was from active region 3386, which was right on the edge of the visible solar disk, so any associated CME was directed away from Earth.
The second event at 2046UTC on the 7th was also from AR3386, which by now had rotated just out of view of the Earth, so again its associated CME was not Earth-directed.
So, we were lucky on both counts. If this sunspot region is still active on its return, we could be in for a rough ride. Keep an eye out from around the 20th of this month when it should reappear.
HF conditions have been variable, with occasional F2-layer openings on the 10m band. The 15m band has produced some good DX including 5W1SA in Samoa on FT8. The 17m band produced Roland, TR8CR in Gabon on CW for Laurie, G3UML. S79KW in the Seychelles was worked by Hugh, EI2HI on 10m SSB, but it has otherwise been quite quiet. Expect more HF DX activity later next month.
Next week, NOAA predicts that the Solar Flux Index will be in the low 160s, with a maximum Kp index of two. If that does pan out, we can expect fairly good HF conditions.
But as always, watch out for solar flares and CMEs that can’t be predicted terribly well. A solar flare could result in a sudden ionospheric disturbance but that would be relatively short-lived. A CME, which might follow a flare in about two days, could see the MUF drop for a day or more.
VHF and up
The brief period of high pressure around the middle of last week will be long gone by the weekend and new Atlantic lows will again dominate the UK weather. At first, this will be mainly over the northern half of Britain before moving to the western side of the country later in the week.
This means that any Tropo at the end of the previous week is not here to stay. The low-pressure input will bring rain scatter propagation modes and, since we are supposedly in the summertime, the rainfall events may be quite heavy or even thundery in places, so there may be good scattering for the GHz bands.
The Sporadic-E season is still simmering with a few brief moments of single hop within Europe, but also some longer multi-hop paths including to the Far East and VK on 10m.
The upper air pattern of jet streams may still be able to trigger a few openings during the coming week, although it is looking much weaker than last week and possibly mainly biased towards northern areas like the Baltic and Scandinavia.
Meteor scatter is one mode that should do well, especially at first with the peak of the Perseids this weekend. It can be quite interesting to monitor the 2m meteor scatter calling channel and stand outside watching for meteors, especially if it’s a bit warmer! The shower has a broad peak so should still provide activity during the coming week.
Lastly, the Sun continues to offer occasional disturbed conditions with a chance of high Kp indices and possible aurora. The easiest solution is to monitor the Kp index and perhaps your favourite Scottish beacon for signs of auroral flutter.
With the Moon at maximum declination this weekend, with long Moon visibility windows, it’s the Microwave EME contest. Moon apogee is next Wednesday so path losses are at their highest until then. 144MHz sky noise is moderate until late Tuesday when the Sun and the Moon are close in the sky until Thursday when levels drop back to low.
Category: GB2RS Propagation News
