Propagation News – 18 August 2024

Last week was notable for its auroral activity, high solar flux index and variable HF conditions.

Monday 12 August saw the Kp index rise to 7 as coronal mass ejection material struck the Earth, sparking visible aurora as far south as Cornwall. But by lunchtime on Tuesday things were back to normal with a Kp index below 2.

The rest of the week remained fairly settled with the occasional blip up to a Kp index of 4. Meanwhile, HF conditions have been variable with N5J on Jarvis Island in the Pacific being the main DX being chased. This has turned out to be a difficult catch for all but the better-equipped stations in the UK.

The operators are active on SSB, CW and FT8, using the SuperFox and Fox and Hound modes, and are working until the 20 August. So, have a listen and give them a call.

The peak times are around 0500 to 1200UTC for a short path contact, and around 1800UTC for a long-path contact. See the website for frequency details and the latest news.

Otherwise, the maximum useable frequency, or MUF, over a 3,000km path has been more than 18MHz and often 21MHz during daylight. Nighttime MUFs have been more than 14MHz when there have been no geomagnetic disturbances.

Next week, NOAA predicts that the solar flux index will start at around 260 but decline to perhaps 210 as the week progresses. This is still enough for some good HF propagation. Predictions are less certain about geomagnetic disturbances, other than a rise on the 22 August.

Solarham.com predicts that a coronal mass ejection associated with an X1.1 solar flare last Wednesday will pass Earth by the 18 August, so we may expect the Kp index to rise today.

VHF and up

The period of alternating hot summer days and unsettled spells with rain or heavy showers looks like the recipe for the coming week.

The weak ridges of high pressure could prove useful for some Tropo on occasions. In the summer months, Tropo is often more pronounced over nearby waters such as the North Sea and south across Biscay or the English Channel. But it can also feature overnight and, if we are lucky, may help with the 23cm UK Activity Contest on Tuesday the 20 August.

These high-summer active fronts or heavy showers can be very good for rain scatter. Since temperature plays an important role in the intensity of summer thunderstorms, the resulting rain scatter is often best in the afternoon and early evening. On rare occasions daytime storms can drift north from France to be over the UK during the night.

The Perseids meteor shower peak has passed now, with some good QSOs reported. It’s a broad shower and there should still be some worthwhile meteor input to play meteor scatter next week.

The recent solar conditions have produced a disturbed Kp index and there were some impressive visible and radio auroras from 10m up to 6m last week. It’s worth watching out for a high Kp index above, say, 6 and be ready to listen for radio aurora in the afternoon.

Lastly, the Sporadic-E season struggles on with varying degrees of success, but it’s still very much a player for another two or three weeks. The upper air charts show that there should be some strong jet streams and thus potentially good sources of the turbulence required for Sporadic-E. Use the link here  NVIS graphs to see if Dourbes in Belgium is showing any spikes.

Moon declination is negative but rising now. It won’t go positive until Wednesday, so short Moon visibility windows and peak elevation continue to increase. Wednesday is also perigee, the Moon’s closest point to Earth and when path losses are at their lowest. 144MHz sky noise is moderate to low over the coming week.

Category: GB2RS Propagation News