Propagation News – 3 June 2018

| June 1, 2018

A large coronal hole on the Sun didn’t affect the HF bands earlier in the last week as its associated high-speed solar wind stream hadn’t had time to reach Earth. However, this was probably the quiet before the geomagnetic storm as the solar material was predicted to reach us at around 450-500km per second sometime around Friday, 1 June.

As the coronal hole is large, and on the Sun’s equator, it is perfectly positioned to deposit a mass of charged particles into the Earth’s magnetic field if its Bz magnetic component is south facing, so enabling coupling. The upshot is that this weekend is probably going to see very unsettled geomagnetic and possibly even auroral conditions. And in view of the hole’s elongated shape we may not see much respite until around Tuesday, 5 June, or even Wednesday, the 6th. So expect lowered maximum usable frequencies, noisy bands and poor conditions as the ionosphere is depleted—not really a good forecast for National Field Day weekend! After Wednesday, 6 June we can probably expect the bands to recover slowly.

The good news is that summer propagation conditions are just about with us, so expect the 20m HF band to remain open longer, perhaps even after sunset, although a lack of decent sunspots is not really helping. The high-speed solar wind may also adversely impact sporadic E formation, so for research purposes keep an eye on 10m over the weekend, but do hear what we have to say in the VHF section about sporadic E too.

VHF and up

Weather-wise it looks like more of the same with high pressure holding on over much of the country, with just the occasional spell when there are likely to be a few heavy thundery showers in the south, chiefly up to this weekend. So this week it’s time to dust off the tropo bands at VHF and UHF and try for those unusually long distance paths, say across the North Sea or south-east into Europe. Remember that paths across the sea can be very reliable from coast to coast, but once a portion of the path crosses the land, the daytime heating can destroy the needed temperature inversions, so they will only work during the night time.

Apart from the odd bit of rain scatter from those early thunderstorms, the other mode of choice will be sporadic E. The season is coming to one of its fabled peaks in early June. Some say it’s to do with extra meteor showers, others not so convinced. Whatever provides the fuel, the weather triggers in the lower atmosphere are what probably controls the location.

In the coming week the main jet stream is out of reach well north of the UK. There may be some weaker jet stream segments towards Spain and, perhaps by midweek, a jet stream over the Norwegian mountains may be useful for a Scandinavian sporadic E opening.

The Moon is at apogee, its furthest distance from earth, this Sunday and declination is negative but increasing. Moon windows will lengthen as the week progresses and losses will fall.

The Arietids meteor shower, the strongest daylight shower of the year, lasts from late May until early July and peaks this Thursday. Look out for enhanced reflections.

Category: GB2RS Propagation News