Propagation News – 20 March 2016

| March 18, 2016

This week has seen continued geomagnetic storms, thanks to a high-speed solar wind stream flowing from a geo-effective coronal hole on the sun’s surface. As we predicted, last weekend was reasonably settled, but then it all went pear shaped. The K-index hit five on Tuesday night, and five again on Wednesday night, this time remaining at five for up to nine hours. High K indices are usually a sign of bad conditions, although there can be highlights.

During the initial phase of a geomagnetic storm you can often get enhanced conditions, but they tend not to last and you can be left with noisy bands and fluttery or no HF signals, especially if they go near the poles.

The noon critical frequency as measured by the RAL Digisonde on Tuesday was 7.2MHz, but just 5.4MHz on Wednesday. Quite a few of the IBP beacons on 14.100 MHz could be heard on Tuesday, but by Thursday morning none were audible.

Next week the solar flux index is predicted to be around 85-95 all week. With no geo-effective coronal holes rotating into view on the sun’s surface the K index is predicted to remain around two. This means we may have more settled HF conditions next week. We suggest you keep your fingers crossed!

VHF and up propagation news

Last week’s high pressure gave some modest tropo openings on the VHF bands, but as hinted at in the last bulletin, it was often handicapped by dry air at the surface, below the inversion. This has the effect of lessening the quality of the ducts formed and makes any tropo weaker and more marginal. It looks like a similar story through the coming week, with the occasional improved spells when the surface layer of air becomes more moist. You’ll know this by the drizzle and misty low cloud.

As always check the bands and look for areas of fog and misty low cloud on the satellite pictures to see which directions might produce the better quality lifts.

Around the March Equinox, is “Fireball season” A fireball is just an especially bright meteor and they seem to appear in greater numbers than usual around this time. In fact, one was reported last week over the UK. Sadly fireballs are no help to meteor scatter operators as they are so few and are short lived.

Conditions were perfect for the Dubus CW EME event last weekend, with the moon at high declination and just beyond perigee.

Next week, losses will increase to maximum as the moon reaches apogee on Friday and windows will shorten, the declination going negative on Wednesday.

Category: GB2RS Propagation News