sabato 24 agosto 2019

Propagation News – 25 August 2019

The last seven days have seen quiet geomagnetic conditions but, equally, zero sunspots and a solar flux index of around 67. Nevertheless, the Lighthouses on the Air event last weekend saw UK stations finding people to talk to, even if real DX was a little thin on the ground.
Saturday, the 17th, saw numerous short-skip openings on 40m that were probably due to sporadic E. Path lengths of less than 150 miles were reported by GB0HL in Norfolk, which meant UK stations were able to talk to others around the country on seven megahertz. This was at a time when the critical frequency, as reported by the Chiltern Digisonde, was only 4.1MHz.

Make the most of any potential sporadic E openings on HF as the season is fast coming to an end. But it will be replaced by better autumnal F2 layer conditions, so it is not all bad news. As the ionosphere cools there will a shift towards more monatomic rather than diatomic species, and these are easier to ionise. As a result we can expect MUFs to rise in late September or early October.

Next week, NOAA predicts the solar flux index will remain around 67-68 and geomagnetic conditions will remain settled until 1 September 2019, when the K-index could rise to five due to material from another solar coronal hole impacting the Earth’s magnetic field. Therefore, after a potential pre-auroral enhancement, expect MUFs to be adversely affected for a couple of days next weekend.

VHF and up:
Microwave bands rain scatter was the main player last week, but it’s looking like we start the period with some high pressure controlling the weather pattern over the UK. This could herald the return of useful tropo conditions. This tropo period should probably last until midweek as temperatures gradually rise to high-summer values before a breakdown, with a chance of thunderstorms from mid-week. It often happens that in very hot weather, the tropo tends to favour sea paths and night-time over the land. The last part of the coming week appears to be heading towards lower pressure with showery weather and cooler conditions, but it should offer some more chances for rain scatter from any big cumulonimbus thunder clouds.

Sporadic E is showing up on 10m on most days, but getting harder to find on 6m. It’s not done yet, but be guided by the clusters and beacons and you should be able to make use of any that does crop up.

One minor meteor shower, the Aurigids, peaks a week today with a zenith hourly rate of six.

With the Moon reaching peak declination this Tuesday, and perigee coming up on Friday, it’s a good week for EME with long daytime Moon windows and lowest path losses.