Propagation News – 19 November 2023

We had another rollercoaster week with periods of reasonably settled geomagnetic conditions followed by more unsettled times. Luckily, it didn’t get too bad, as it did when the Kp index hit seven the week before.

This, coupled with a lower solar flux index of 119 on Thursday, has meant HF conditions have not been outstanding. However, we are still buoyed by the seasonal HF conditions, which are generally good in autumn.

Propquest shows that the F2-layer critical frequency is still maxing out at more than 12MHz around noon. The F2-layer critical frequency is the highest at which radio waves are returned back to Earth when sent directly up into the ionosphere.

This gives us a maximum usable frequency (MUF) over a 3,000km path of more than 40MHz. Interestingly, it also gives us an MUF over a 500km path of more than 14.7MHz. So, look out for long distance inter-G signals around noon, or thereabouts, on the 20m band. The 30m band remains a pretty solid inter-G band from late morning to mid-afternoon.

Getting back to the geomagnetic conditions, the Bz component of the interplanetary magnetic field (IMF) has been pointing south for long periods which is why the Kp index has been higher than normal. This means the IMF more easily couples to the Earth’s magnetic field, just like two bar magnets aligned north against south.

Next week, NOAA predicts the solar flux index will rise again, perhaps reaching 140 by the end of the week. However, it also forecasts unsettled geomagnetic conditions from the 22nd to the 25th, with a forecast Kp index of up to 5. So get your HF DXing in early next week!

VHF and up

The seemingly never-ending period of unsettled weather is likely to continue into the coming week.

This means another week with only a limited chance of tropo for most parts of the country. As something of a long shot, it’s worth noting that southern parts of England, especially along the Channel coast, may have access to higher pressure over Biscay after the middle of next week for chance tropo paths south into western France or northern Spain.

For the rest of us, the weather pattern is rather changeable with a tendency for north-westerly winds. At this time of year, this can often mean that showers form over the surrounding seas. Rain scatter options could be worth checking for stations around the Irish and North Sea coasts.

Meteor scatter is also worth considering in view of the peak of the Leonids, on Friday the 17th and Saturday the 18th, at the beginning of this first weekend. It’s quite a broad period of activity and, with the minor Moncerotids shower peaking on the 22nd, conditions could still be good throughout the new week.

Lastly, a thought about the chances of aurora and the busy solar activity; it’s worth keeping a check on the planetary Kp index for signs of aurora—look for a Kp above six.

For EME operators, Moon declination starts at a minimum but rises all week, going positive again late on Wednesday. Losses are at their lowest with Moon perigee on Tuesday the 21st. 144MHz sky noise is low all week. Perigee is when the Moon is at its closest point to Earth.

Category: GB2RS Propagation News