Propagation News – 26 March 2017

Last week’s predicted geomagnetic storm materialised on cue, sending the K index up to five on Tuesday. The storming continued right through Wednesday into Thursday. There was an initial ionospheric enhancement late on Tuesday, but it didn’t last long. Maximum useable frequencies were then adversely affected on Wednesday with noisy bands and even 20 metres struggling to open at times. The culprit was a high-speed stream from a solar coronal hole, which impacted the Earth at speeds in excess of 650 kilometres per second, triggering an aurora. The time around the equinoxes can often bring more auroral activity.

The sun has been otherwise quiet, with only one tiny sunspot group coming around the limb.

Next week, NOAA predicts that the solar flux index will remain in the low 70s, but geomagnetic disturbances will continue. The K index is predicted to rise sharply on Tuesday due to yet another high speed stream from a coronal hole. This may push the K index up to six, prompting auroral conditions yet again.

Poor conditions may then continue, so look out for an initial positive phase, which could occur early in the week, but then expect disturbed conditions with lower maximum usable frequencies for the remainder. As always, polar HF paths may be the worst hit, while North-South paths could remain less affected.

VHF and up

The high pressure we hinted at last week is now building over northern Britain and should dominate the weather for much of the coming week.

The prospects for tropospheric openings look good, especially across the North Sea into northern Germany and the Low Countries. Weather models seem to follow a theme that the high declines later in the week with low pressure and the potential for gigahertz bands rain scatter for western areas by next weekend.

As we move towards April, there will be a chance of some early season Sporadic-E within southern Europe. This is not ready for us yet, but a sign of good times ahead, given another three weeks or so. Now is the time to be checking those 10m, 6m, 4m and 2m beams and beacon lists.

Moon declination goes positive this week, meaning increasing windows of moon visibility. With perigee on Thursday, losses will become lower as the week progresses, making it a good week for EME.

Category: GB2RS Propagation News