venerdì 1 febbraio 2019

Propagation News – 3 February 2019

Last week was a mixed bag in terms of HF propagation. The solar flux index was a little higher at 74, helped by a sunspot group that has now rotated out of view. Geomagnetic conditions were very settled in the first half of the week with the Kp index often sitting at zero. It seems quite a while since the index was this low.

But that couldn’t last as a very large elongated coronal hole on the Sun’s equator threatened the Earth with an enhanced solar wind. This eventually came to fruition on Thursday afternoon, pushing the Kp index to three at first and then five overnight, bringing minor G1 geomagnetic storming at higher latitudes. At the time of writing this looks like it is likely to bring continued unsettled HF conditions across the weekend, complete with depressed maximum useable frequencies.

NOAA predicts a solar flux index around 72 next week as the solar minimum continues. The good news is that once the effects of this coronal hole disappear we can expect more settled geomagnetic conditions and a return to seasonal averages when it comes to maximum usable frequencies.

The low bands are still at their optimum, with 160, 80 and 40m providing good propagation opportunities. Sixty metres, or the 5MHz band, is also providing inter-G and European contacts during the day, as the critical frequency is often sufficient to support propagation on the band.

Higher up, 20 metres is still the best band for reliable DX, although it tends to open late and close early at the moment, with occasional openings on 17m and perhaps even 15m.

VHF and up:
It’s looking like a week to be getting on with those hardware and software projects in the warmth of the workshop while keeping an eye on the VHF DX clusters. Cold and unsettled would describe the first part of the week, with limited options for tropo due to some wintry areas of low pressure. There are signs of a weak ridge of high pressure to the south of Britain at the start of the week, but this offers only marginal chances for paths to the south from southern England into the continent and Spain.

With the solar conditions, the weekend is looking likely to offer some chances of aurora due to the large coronal hole, so even if tropo is not a strong contender, there are still some possible interests for VHF ops. For GHz bands enthusiasts, the snow showers early on may provide some rain scatter.

The Moon is at apogee on Tuesday and declination is negative, but rising all week. Moon windows will lengthen as the week progresses, but path losses will be at their highest.

One minor meteor shower occurs on the eighth, the Alpha Centaurids, but with a Zenithal Houry Rate of just six it’s not really a significant one for meteor scatter operation.