Propagation News – 19 May 2019

| May 17, 2019

Last week saw the Kp index rise to seven on Tuesday, thanks to an enhanced solar wind stream containing a sharply south-pointing Bz. This is the direction of the interplanetary magnetic field and south-pointing means it was more likely to couple with the Earth’s magnetic field. This was due to a number of filament eruptions in the vicinity of sunspot region 2741.

While not entirely unexpected, the Kp index rise to seven was quite severe and resulted in auroral conditions on HF. A number of B-class solar flares on Wednesday didn’t help much either. The FoF2 plot at looked a bit like a roller coaster as the predicted MUF over a 3,000km path went rapidly from nearly 20MHz to 16MHz. Luckily, things were more settled on Thursday with a Kp index of two, although HF conditions remained flat.

Sunspot group 2741 is now rotating off the Sun’s disk, with NOAA predicting the solar flux index will go back down to around 68 next week, due to an absence of spots. As a result the K-index is predicted to be around two to three as the risk of coronal mass ejections declines.

Phil, GU0SUP, the RSGB newsreader for Guernsey, reports that FT8 has been quite active. On the morning of Friday, the 10th, he heard lots of Ws on 30 metres, including a W7 in Idaho. Moving to 20m he then then saw K2GT calling CQ and found out he was in Hawaii. Phil says he was very surprised at just how loud he was. He adds that he usually expect to work KH6 later in the day, although he has worked Hawaii in the mornings before, but when the SFI was much higher.

VHF and up

The weak high pressure nearby may reassert itself as a shallow area of low pressure over France drifts away. This does not look anything like as strong as the exceptional high of 1042mb of last week. Therefore some weak tropo is always possible, especially along the east coast.

Sporadic E has been doing fairly well with a comprehensive selection of jet streams to offer potential triggers for sporadic E at first, but the coming week looks much thinner with the main jet stream activity displaced south over the Mediterranean. This may put sporadic E patches too far south, although it should be productive across the Mediterranean region. Best prospects from the UK look to be south into Spain and Portugal.

As we head down to minimum Moon declination on Wednesday and are just a weak away from apogee, Moon windows are short and losses high. It’s a good time put aside QSO attempts and to check out EME system performance using Sun to cold sky measurements as the sun is nice and high in the sky at noon now.

There is no significant meteor shower activity this week so in between the sporadic E, keep looking for the early morning random meteor peak on the lower VHF bands.

Category: GB2RS Propagation News