Propagation News – 17 December 2023

We had a fairly settled time last week with only the solar wind and some solar flare activity to contend with.

Sunspot region 3514 produced a moderately strong M5.8 solar flare on the 14 December. This event was responsible for a coronal mass ejection, or CME, but that was directed to the west and missed the Earth.

The problem with the solar wind is that its Bz has mostly been pointing south, which means it more easily couples with the Earth’s magnetic field allowing solar plasma to flood in. The result was that the Kp index mostly remained high, with the index hitting three or four across the midweek period.

While not excessive, this has affected HF to an extent, although the daytime MUF over 3,000km has remained above 28MHz on most days.

What you may find is that the higher bands are now closed until later in the morning and that they close earlier in the afternoon as well. This is partly due to the time of year and partly due to the lower solar flux index we are experiencing.

The solar flux index improved slightly over the past week, ending at 135 on Thursday, having been in the 120s earlier.

Next week NOAA predicts that the solar flux index will be in the range of 125 to 140. It is predicting unsettled geomagnetic conditions from the 16 to the 19 December, with a maximum Kp index of five.

Now for a propagation forecast. Santa’s broadcasting arm, Santa Radio OF9X, is active again from near the Arctic Circle on all amateur radio bands, using CW, SSB and FT8, until the end of the year. The activity is organised by the Radio Club of Pusula, OH9W and Radio Arcala, OH8X.

Keep an eye on DXSummit.fi to find out where they are operating. So far, they have been spotted on the 160, 40, 20, 12 and 10m bands. The Proppy prediction chart shows that anywhere between 10MHz and 28MHz is fair game during daylight, while 7MHz and below will work better at night.

VHF and up

As expected, the return of a significant region of high pressure developing over the continent as this week ends, will bring some enhanced Tropo conditions from southern UK into the continent and across Biscay to northern Spain.

It is also possible that the traditionally preferred policy of beaming around the edge of a high for DX paths will make looking east into northern Germany, Poland and the Baltic a fair prospect, but only until around Tuesday 19 December when a cold front moves south and breaks the path. This is a pity since it will be before Tuesday’s 1.3GHz Contest and Thursday’s 70MHz UK Activity Contest, which look like missing the best conditions.

The second half of the coming week will be dominated by low pressure to the north of Britain and a series of fronts and showery troughs driving south, bringing much colder air with a risk of wintry weather. It will also become very windy at times.

This removes Tropo from the picture, but rain scatter may be worth considering, although the shower echo regions will be moving briskly. Use online rain radar displays to help you.

The other modes of meteor scatter and aurora are worth leaving on the list with the remains of the December Geminids still with us.

Don’t forget that out-of-season Sporadic-E propagation often appears in the period from mid-December to mid-January, so check the 10 and 6m bands periodically for activity.

For EME operators, Moon declination is negative but rising, going positive on Wednesday 20 December. Path losses are at a minimum at perigee, the Moon’s closest point – this was on Saturday 16 December. 144MHz sky noise is low all week.

Category: GB2RS Propagation News