Propagation News – 11 August 2019

Matter from a solar coronal hole hit the Earth last week as predicted. However, we got the date wrong, as it actually impacted us on Monday and not Sunday, as it was moving slightly slower than we thought. This sent the Kp index up to five as the Earth’s geomagnetic field was disturbed and where it stayed for four consecutive Kp sessions, or 12 hours in total. There were reports of a pre-auroral enhancement on 10 metres, but overall HF conditions were down as a result.

Tuesday was characterised by reduced maximum usable frequencies, but by Wednesday the solar wind stream had calmed down and the ionosphere soon got back to its normal sunspot minimum doldrums. There was DX to be chased though, with the CY9C St Paul Island DXpedition off Nova Scotia being workable on the lower HF bands, especially 20m, and being very audible in the UK.

Next week NOAA predicts a calm Sun with a solar flux index of 67 and zero sunspots. After potentially unsettled geomagnetic conditions this weekend due to a coronal hole, the rest of the week should be fine, with a maximum Kp index of two or three.

Don’t forget that it is International Lighthouse and Lightship Weekend on the 17th and 18th, which should attract more than 500 lighthouse entries located in over 40 countries. A full list can be found at illw.net, but please note that with ionospheric conditions the way they are you may struggle to work nearby UK lighthouses on 40m due to the low critical frequency, and 80m may be closed from mid-morning until late afternoon due to D-layer absorption. But feel free to try for the European stations and those further afield on 40 and 20m.

VHF and up

The next week or so is looking decidedly unlike summer with a tendency for low pressure, especially in the north. Wind, rain, thunder and no tropo is hard to sell, but there are usually some positives even in bad weather! Let’s start with a strong positive, which is a good jet stream pattern for sporadic E. In this case a marked upper trough crosses the country with segments of strong jet stream winds over the UK and near continent. In the closing weeks of the sporadic E season, a strong jet stream is a real bonus, so pursue the usual summer operating rules and check the 10m and 6m bands late morning and late afternoon.

Another positive is that the Perseids meteor shower is approaching its peak, so expect excellent meteor scatter conditions over the coming days. The broad peak of 11 to 13 August may cause meteor ionisation, which is an important component in the formation of sporadic E.

Now the bad news. There is pretty much a total absence of high pressure, so it’s unlikely that tropo will feature much, if at all. Strong winds will remind us to check the antennas are in good shape for winter. Trying to end on a positive note, thunderstorms are useful if you are into GHz bands rain scatter from the large cumulonimbus clouds.

Moon declination is at its minimum, most negative, today, so the Moon will be very low in the sky at its zenith. Losses are still increasing as we approach apogee on Saturday, so it’s a poor week for EME.

Category: GB2RS Propagation News