Propagation News – 22 March 2020

| March 20, 2020

Last week saw a continuation of the zero sunspot regime we’ve been seeing for the past few months. The solar flux index remained in the range 70-72, with settled geomagnetic conditions and with the Kp index remaining in the range of one to two. Thursday the 19th was the exception, when the Kp index rose to four between midnight and 0300. This was undoubtedly due to a high-speed stream from a returning solar coronal hole, but it was relatively short lived. The critical frequency graphs at show that this had minimal adverse effects.

This weekend marks the spring equinox, which is normally a good time for HF conditions. With equal illumination on both hemispheres, it is a good time for north-south paths such as the UK to South Africa, and the UK to South America. shows that you probably have a 30-40% chance of making an FT8 contact with South Africa on 14MHz, perhaps even 18MHz, around 1600UTC this month. The path to Buenos Aires on 14MHz is similar, being optimum around 1900- 2000UTC.

Next week NOAA predicts more of the same, with the solar flux index remaining around 70. Geomagnetic conditions should remain settled, other than on Friday the 27th when the Kp index is predicted to rise to four.

VHF and up

The coming week appears to be dominated by high pressure, so this will bring a chance of Tropo to many parts of the country, although it’s not a very favourable-looking feature in a Tropo sense. There are three phases to this period. First, this weekend we are in the easterly flow, probably fairly dry air so not necessarily a good Tropo spell, especially with the brisk southeasterly winds.
Secondly, into next week a cold front moves into northwest Britain and drifts southeast, disrupting the high pressure and any potential Tropo.

The third phase, from midweek, sees the cold front weaken and high pressure build again as a weak ridge across the country, which remains into next weekend. This may be a better prospect for Tropo, but still not a strong steer.

As for the other exotic modes, Sporadic-E seems a relatively low probability and rain scatter in high pressure also tends to be rare. That just leaves the spring preference for aurora to keep us hopeful.

We have a daytime Moon all week, with declination going positive again on Tuesday. Peak Moon elevations will continue to increase, but with apogee also on Tuesday, path losses are at their highest for the Lunar Month. 144MHz sky noise is low all week.

With no major meteor showers due until the Lyrids at the end of April now, just keep looking for random meteor scatter QSOs around dawn.

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

Category: GB2RS Propagation News