RSGB
June 26, 2025
The last week was good from a geomagnetic disturbance point of view. Up until Wednesday, the 25th, the Kp index had not been higher than 3.67, and had mostly been in the ones and twos. This helped HF propagation to a great extent.
Sunspots have been present with the solar flux index sitting at 120 on Wednesday, the 25th. A look at the visible disk at solarham.com shows five sunspot groups facing Earth. None are groundbreaking, but they are at least helping to keep the solar flux index relatively high.
Daytime F2 MUFs over a 3,000km path have been reaching 18MHz and even 21MHz at times, with 14MHz being more reliable. Sporadic E continues to make 28MHz a useful band for short-skip, with much of Europe being workable mid-morning on the 25th, at least using FT8.
Estonia, Germany, Poland, and Finland were all easily worked on FT8, but nothing was heard on the usual 10m CW and SSB frequencies.
Next week, NOAA predicts that the solar flux index will be in the 140 to 150 range. Unsettled geomagnetic conditions are forecast for 1 to 3 July, when the Kp index could reach 4. Conditions may become unsettled again on the 6th and 7th again with a predicted Kp index of 4.
But in the meantime, make the most of the sporadic E on the 10m band, as it won’t last forever!
VHF and up propagation news from G3YLA and G4BAO :
The more traditional summer weather, with patchy rain and showers, is likely to continue for a bit longer. The more persistent rain is likely in the north closer to low pressure near Iceland, whereas the rain may be more intermittent in southern areas, closer to high pressure over France.
This probably rules out any significant tropo in northern Britain over the coming week but does allow for the occasional enhancement in the southern half of the country. Most areas will have some rain scatter opportunities for the GHz band operators—although perhaps fewer in the south than in the north.
The solar conditions have quietened down a little in terms of aurora recently but, as we said last week, don’t forget to look north in the twilight sky for signs of the pale noctilucent cloud. This is a high summer phenomenon. See if you can detect any wave patterns—like ripples on a sandy beach—in the cloud.
The month of June tends to be quite good for meteor input and the last of the set, the June Bootids, peaked on Friday, the 27th. So, there should be some good chances for hearing the odd ping or two, or even seeing one in the evening sky after dusk.
The primary mode of interest is still sporadic E, which is in full swing and doubtless being topped up by the Bootids meteors, which produce the main ingredient of sporadic E propagation—long-lived ions—as they ablate, or burn up, upon entering the atmosphere.
In terms of the usual search for placement of sporadic E events geographically, the main jet stream interest is likely to be across the northern part of Europe for the coming week. This suggests trying paths to Scandinavia and the Baltic states, whereas for triggers due to upper air ridge patterns use the more southern routes.
The Moon has passed perigee for this month, so path losses are rising. Moon declination is still high, not going negative until Tuesday, 1 July. 144MHz sky noise is low, increasing to moderate by next weekend.
(Mike Terry/BDXC)