Propagation News – 1 September 2024

We had a good week for HF propagation, at least until we had a Kp index of 5.67 on Wednesday, the 28th. This was caused by the Bz component of the interplanetary magnetic field moving into a south-pointing position.

Luckily, it didn’t last long and geomagnetic conditions were back to normal by Thursday.

The solar flux index remains above 200 with no sign of it dropping. But solar flare activity has not diminished either with 16 M-class flares over the past seven days and more than 60 C-class events. There remains a 55 percent chance of a further M-class flare and a 10 percent chance of an X-class event.

Tuesday, the 27th, saw some good activity on the upper HF bands with the 10m band opening up at times. VK has been heard on 28MHz in the mornings, which bodes well for the coming months.

The top DX choice this week has been CY9C on Saint Paul Island near Newfoundland. The team is active on all bands until 5 September using CW, SSB, FT8, Super Fox and RTTY. VOACAP Online shows that the 20 and 17m bands offer the best chance for a contact and are open from 0900 to 2000UTC. The 30m band is another strong contender from 2000 to 1000UTC.

Next week, NOAA predicts that the solar flux index will start at around 250 but could end the week at 275. As always, it estimates the Kp index will be at 2 all week, but this will depend upon coronal mass ejections, so keep an eye on solarham.com for daily updates.

If a solar flare and associated coronal mass ejection does occur, expect the Kp index to rise after about 48 hours, with a lowering of the maximum useable frequency.

VHF and up propagation news from G3YLA and G4BAO

The autumn season usually brings thoughts of tropo, since areas of high pressure can often be a feature of this time of year. Most models predict that there will be high pressure moving in to offer tropo conditions on Sunday, 1 September.

Thereafter, the models differ, and some bring low pressure over the country for much of the coming week, while others maintain a high-pressure story and the continuation of tropo.

This is potentially useful for the 144MHz UK Activity Contest on Tuesday and Wednesday and, if it lasts, the 144MHz Trophy Contest next weekend along with the Backpackers Contest on Sunday, 8 September.

With the uncertain feel to the forecast at the moment, we may find rain scatter is the main option on the GHz bands.

Meteor scatter is again reduced to non-shower random events with just a minor shower, the Aurigids, peaking on 31 August. This shower has produced brief unexpected outbursts with a zenithal hourly rate of around 30 to 50 per hour in 1935, 1986, 1994 and 2019.

Random meteor flux is at its annual maximum in September with relatively good rates, especially during morning hours. Pre-dawn is the best time to try.

The solar conditions continue to provide chance auroras. Keep one eye on the Kp index and lock the frequency of some northern European beacons into your rig’s memory.

Lastly, it’s the nominal end of the 2024 summer sporadic E season and the daily blogs on Propquest have finished. However, some years can produce surprise sporadic E events during the first week of September.

Moon declination starts the weekend still high but falling, going negative again on Thursday, the 5th. So, Moon visibility windows will also fall, as will peak Moon elevation.

Moon apogee is also next Thursday so path losses are still increasing. 144MHz sky noise is low until Monday but, shortly after moonrise that day, the Sun and the Moon become close in the sky and continue to be until after moonset on Tuesday.

This means sky noise will be very high, especially at VHF, due to wide antenna beamwidths.

Category: GB2RS Propagation News