venerdì 29 gennaio 2021

Propagation News – 31 January 2021

We are almost into February and still the Sun is not playing ball in terms of sunspots. This week saw groups 2797, 2799 and 2800 rotate out of view, but all were minuscule and didn’t contribute much. The solar flux index was 76 on Thursday with a sunspot number of 26. There is a plage area, which can be a precursor to sunspots, at the same latitude as group 2800, but we will have to wait and see what develops.

The STEREO Ahead spacecraft view shows little of note other than a coronal hole that will eventually become Earth-facing.

There was a geomagnetic storm late on Monday and in the early hours of Tuesday, which was caused by a high-speed stream from a coronal hole that we warned you about last week.

This week’s highlights have been short FT8 openings on 10 metres, possibly due to mid-Winter Sporadic-E. The French Alps, Poland, Ireland and Spain have all been spotted, and short F2-layer openings to Mauritius in the morning and Paraquay in the afternoon kept interest levels up. These winter Es openings are becoming rarer and shorter, but it is still worth keeping an eye on 10m.

Otherwise, the lower bands have brought the most action with 40 and 80m still providing good activity after dark.

With little scope for sunspots, NOAA predicts the SFI will be in the mid-70s next week. Unsettled geomagnetic conditions are forecast for Sunday or Monday, due to yet another high-speed stream from a coronal hole, which became Earth facing on Friday. The Kp index could rise to three or four, but once it passes the Kp index may be down to two.

Daytime MUFs over a 3,000km path are currently exceeding 21MHz during the daytime. Night-time critical frequencies of around 2.9-3.5MHz mean that 80m is marginal for local contacts at night while remaining fairly solid for European paths and DX.

VHF and up:

It looks like satellites will offer the best chance of working VHF DX, with not many prospects for Tropo, as the unsettled theme continues to drive our weather over the next week or so. The south and west of the British Isles, along with the north-eastern areas, will have some temporary weak ridges ahead of slowly-advancing Atlantic systems.

Overall then, with some borderline snow events on the northern edge of the rain areas, there could be some winter scatter options for the microwave bands, but otherwise another thin week.

Some models do introduce a weak ridge of high pressure over the country at the very end of next week, but this is not to be relied upon this far out, and probably with dry cold air near the surface it is not such a good prospect for Tropo.

Moon declination goes negative on Tuesday so as the week progresses, Moon windows will shorten and peak Moon elevations will fall. Perigee is on Wednesday, so path losses are at their lowest this week. 144 MHz Sky noise is moderate, but becomes high this coming weekend.

The Alpha Centaurids meteor shower is just over a week away so you may see some small improvement in meteor scatter conditions, but with a zenith hourly rate (ZHR) of just six, don’t expect any fireworks.

And that’s all from the propagation team this week. (