Propagation News – 12 December 2021

The predicted elevated Kp index that we talked about last week didn’t amount to much at the end of the day. The solar wind remained reasonably calm and the Kp index only peaked at three. This rapidly fell to one by Tuesday and stayed at one or two for the rest of the week.

Solar activity has also been quiet, with the solar flux index falling to the high 70s on Tuesday, where it remained until at least Thursday the 9th. In fact, on Thursday there were zero sunspots and an SFI of 77. Looking at the STEREO Ahead spacecraft data shows very little activity turning into view and, as a result, the NOAA forecast is for only a slight increase in the SFI to the low 80s, perhaps climbing to 87 by the end of next week. It is not surprising, therefore, that Propquest is showing that the extrapolated MUF over a 3,000km path is often below 21MHz during daytime.

The long-range forecast from the US Air Force is for the SFI to remain below 90, at least until the third week in January, so get used to operating in this low SFI domain for a while longer. The good news is that sunspots can appear at any time, so our forecast may be inaccurate. Let’s hope so!

VHF and up

We are fighting our way through a very disturbed weather pattern, and the unsettled pattern over this weekend will bring some rain scatter possibilities, but as it’s winter, these may not produce the DX like summer storms do. Often local rain overhead produces strong rain scatter signals from relatively local stations that seem independent of beam heading.

There are signs of high pressure returning during next week, so hopefully not long to wait for tropo now. There are signs that from Tuesday, a stronger build of pressure will occur. Initially this will be over the south of the country, but gradually extend to northern areas during the second part of the week. This will bring some good Tropo opportunities, especially into the near continent and across the North Sea to southern Scandinavia.

Meteor scatter and aurora are always worth checking, but the key one to focus upon this week will be the Geminids meteor shower that peaks on Monday night, the 13th to 14th. Expect plenty of strong bursts, especially in the early hours of the 14th.

Moon declination goes positive again on Sunday so the EME week will be characterised by lengthening Moon windows and increasing peak Moon elevations, which occur later in the evening. The Moon reaches apogee next Saturday so path losses will be at their highest. 144MHz sky noise will be low for most of the week.

Category: GB2RS Propagation News