Propagation News – 15 April 2018

| April 13, 2018

The predicted unsettled geomagnetic conditions arrived on Tuesday and continued with the K-index hitting five on Wednesday. This was due an elongated coronal hole on the Sun, with the escaping plasma causing the solar wind to pick up in both speed and density. The wind peaked at more than 550 kilometres per second and widespread visual aurora were reported at high latitudes.

There was a brief ionospheric enhancement on Tuesday evening that saw the critical frequency rise to more than 5 MHz, with the predicted MUF reaching 18 MHz around 1900 UTC. But maximum usable frequencies struggled to get to 14 MHz on Wednesday during the subsequent ionospheric storm. This shows that we can get a brief ionospheric enhancement as the solar material first hits, so it is worth watching the bands.

Otherwise, the Sun remained spotless with the solar flux index sitting in the high sixties.

Next week the solar flux index will remain around 67 and HF propagation will largely be dominated by solar wind effects again. NOAA predicts reasonably settled conditions for the first half of the week, but unsettled conditions again from around the 19th.

As we’ll describe in the VHF section, sporadic E may start to show quite soon, and this can affect all the upper HF bands with strong, but often brief short-skip propagation into Europe.

VHF and up

The cold misty weather across the northern North Sea into the Baltic may have set up a few tropo paths, but so far it has seemed fairly quiet. This initial phase of the Scandinavian high will decline over the weekend, but early next week the high will rebuild over the North Sea. It will be better placed and could be more useful during the rest of the week for tropo along the east coast, say from East Anglia to north-east Scotland and eastwards across the North Sea to the Low Countries.

There will also be some occasional thundery developments, mainly in the lead up to this weekend with a hint of potential rain scatter on the Gigahertz bands.

It is mid-April and the 2018 sporadic E season beckons, so it is worth repeating a few basic rules to help those who have never worked it before. Start by checking the European beacons on 10m and 6m during the morning and late afternoon. A classic opening will usually have two phases, one say from 1000 to 1200 UTC and a second in the late afternoon and early evening from 1600 to 1900 UTC. Of course it can happen at other times, so put 10m and 6m in your shack routine during these summer months. Keep QSOs brief, so report and locator will do in these transient events.

April also brings increased meteor activity. The first significant shower, the Lyrids, peaks on 22 April, sometime between 1000 and 2100 UTC.

Moon declination is positive and increasing this week and the Moon is at perigee again on Friday at 368,717km from the earth. It is a good week for EME then, with long windows and high Moon elevations, meaning low ground noise with low path losses.

Category: GB2RS Propagation News