Propagation News – 1 October 2023

| September 29, 2023

Another week of disrupted solar and geomagnetic conditions saw the Kp index go up and MUFs come down.

A period of minor G1 geomagnetic storming was observed on Tuesday the 26 September thanks to an enhanced solar wind stream containing a long-duration southward-facing Bz component. If the solar wind’s Bz magnetic field points south, it more easily couples with the Earth’s magnetic field, allowing solar plasma to flood in.

The net result was a Kp index of 5.67 and visible aurora seen from the UK once again. It is worth reminding people that, at this point in the solar cycle, conditions are being governed more by the Kp index than the solar flux index.

A high Kp index generally results in lower MUFs and poor HF conditions.

During the week, the solar flux index was around 175, declining to 156 on Thursday 28 September. The number of solar flares also decreased as the week progressed. Next week NOAA predicts that the solar flux index will remain in the range 145 to 155, perhaps hitting 160 on the 7 October.

NOAA also predicts quiet geomagnetic conditions with a maximum Kp index of 2. As we said last week, at this point in the cycle solar flares and coronal mass ejections are very prevalent and hard to predict. So, do not be surprised if the Kp index goes up again.

Otherwise, if it remains low, make the most of the good HF conditions that generally follow.

Finally, as it is now October, we can expect another step up in HF conditions as we enter Autumn, so keep an eye on the 10m band, which should be opening up to the US and Canada in the afternoon. There are plenty of 10m beacons to listen for from 28.160 to 28.330MHz, as well as FM repeaters clustered around 29.600MHz.

VHF and up

Last week saw trans-equatorial openings on 50MHz with V51 Namibia reported all over the UK, as far north as Scotland around 1900UTC.

On the tropo front, last week was fairly unsettled with a visit from Agnes, our first named storm of the season, which affected the north and west.

The coming week is looking much more suitable for VHF radio with high pressure building over the country from Tuesday, bringing a good chance of Tropo as we go through the week.

This may not be fully developed for the 144MHz UK Activity Contest on Tuesday 3 October, but possibly starting to help lift conditions, in the south at least.

The high pressure will become more widespread over the next week, but by the following weekend of the 7 and 8 October, the 1.3GHz Trophy may have to deal with more disturbed conditions in western areas. However, conditions will still probably be good for eastern areas across the North Sea to southern Scandinavia.

The meteor scatter prospects are improving as we move towards the October Draconids, which peak on the night of the 8 and 9 October. Auroras have also featured recently so should remain in our checklist.

Incidentally, although we are technically outside the main Sporadic-E season, Dourbes ionosonde data plotted on the Propquest website have shown occasional ‘blips’ in the critical frequency of the Sporadic-E layer, for example to 7.5MHz around 1650UTC on Wednesday 27 September. This would certainly be enough for 10m and perhaps even 6m chance openings. ‘If in doubt call CQ’ is the take-away message here.

Moon declination goes positive on Friday 29 September and reaches its peak the following Thursday. This means increasing Moon elevation and lengthening Moon Windows until then. The downside being that path losses are increasing all week ahead of apogee on the 10 October.

144MHz sky noise starts off low, increasing to 500 Kelvin next Thursday before dropping again for the weekend.

Category: GB2RS Propagation News