Propagation News – 10 November 2024

We had another week of high solar flux and good conditions on HF.

Solar activity remained at high levels thanks to an impulsive X2.3 solar flare around active region 3883 at 13:40 UTC on the 6 November, but the event was not responsible for a coronal mass ejection (CME).

The Kp index remained below 4.5 all week, with a solar flux index in the range 240-260. That was more than enough to keep the ionosphere very active.

A recent report on spaceweather.com  suggested that the solar cycle may have peaked in the Sun’s southern hemisphere but may still have a way to go in its northern hemisphere.

It’s usual for there to be two peaks in a solar cycle as the two hemispheres are seldom synchronised. We will have to wait and see, but it could mean another three to six months of high SFI numbers as the northern hemisphere catches up.

A solar filament located in the southwest quadrant erupted on the 7 November. A coronal mass ejection, or CME as it is also known, occurred but appeared to be off the Sun-Earth line, so no major impacts are expected.

A sunspot group turning into view from off the southeastern limb has been assigned active region 3889 and is producing M-class solar flares. The probability of further M-class flares stands at 80%. Meanwhile, the risk of an X-class flare currently stands at 35%.

A coronal hole is currently Earth-facing and could cause some disruption sometime around Saturday 9 November.

The solar proton flux has decreased to normal levels, so polar paths should now be unaffected.

Next week, NOAA predicts that the SFI could decline into the range 165-185. Geomagnetic disturbances are forecast for the 11th and 12th, and again on the 15th, with the Kp index predicted to reach four.

Meanwhile, we do urge you to get on 10 metres, which is currently experiencing some fine DX openings. This month and next will probably give the best chance of good 10-metre propagation for a while.

 VHF and up

Another week has just passed with daily F2-layer propagation on 50MHz providing morning openings to Southeast Asia, and the Americas in the afternoon. Expect more in the coming week.

The current spell of high pressure has had a good run with some excellent Tropo conditions, with the best DX along the side of the high pressure.

This weekend will see the high finally giving way as weak Atlantic fronts move in from the west. This will soon be replaced by a new high building in the colder air behind the weekend fronts. It may look like Tropo should come back, but this high may be less productive.

The major change of weather pattern comes before mid-week, when it may turn more unsettled as low pressure moves closer to eastern areas from the North Sea. This general move towards more unsettled conditions will continue through the end of the week.

In terms of propagation, good Tropo will be replaced by some patchy rain scatter opportunities for the GHz bands from about the middle of next week.

Staying with scatter modes, meteor scatter looks promising with the Taurids peaking on Tuesday 12 November and the Leonids due to peak on the following weekend on Sunday 17 November.

The solar conditions continue to offer chance occurrences of aurora due to solar flares or CMEs so, as usual, keep a watch on the Kp index going above Kp=4.

An occasional reminder of the possibility of out-of-season Es for the digital modes is timely. Recently the critical frequency of the Es layer has reached 7MHz on the Dourbes ionosonde plotted on www.propquest.co.uk  and in theory this would be good enough for a 6m band path.

For EME operators, Moon declination is negative but rising, going positive again on Tuesday 12 November. Path losses are falling as we approach perigee next Thursday 14 November. 144MHz sky noise is moderate to low this coming week.

Category: GB2RS Propagation News