via the RSGB: Propagation News – 3 June 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.

Read more – via Radio Society of Great Britain – Main Site