domenica 2 ottobre 2016

Propagation News – 2 October 2016

Last week was dominated by extensive geomagnetic disturbances thanks to ongoing coronal hole activity on the sun. Coronal holes are areas with open magnetic field lines that allow plasma to escape as a high-speed stream. This plasma impacted the Earth causing aurora and unsettled HF conditions, especially on paths over the poles.

The K-index was pushed up to five and even six throughout the latter half of the week, bringing a mixed bag of HF propagation.
At times the maximum usable frequency was suppressed with noisy HF bands and very poor propagation. But there were highlights, with enhanced HF propagation at times, up to and including 21MHz. DX heard in the UK included D66D Comoros and S9BT Sao Tome.

Next week NOAA predicts very unsettled geomagnetic conditions for Sunday, 2 October and the first half of the week and unsettled conditions for the remainder. The solar flux index will be in the range 80-85, with a chance for C-class solar flare activity.

Because of the way HF conditions can change quickly, we suggest keeping a close eye on the 20 to 15 metre bands as short-lived openings may occur at any time during daylight hours. As we head into October, DX is being worked and conditions will continue to improve.

VHF and up propagation:

The end of last week saw the finish to very unsettled weather. This week, high pressure is due to build to the east of Britain over Scandinavia and eventually link up with another area of high pressure over Biscay. This should provide some modest tropo prospects at times for many areas, although Ireland and western Scotland may remain too breezy for any significant inversions to develop. The limiting factor of the tropo may well prove to be fairly dry low-level air under the inversion, so the better conditions will be seen when there is evidence of moisture near the surface, like fog and mist.

Wednesday sees the Draconids meteor shower. Don’t get too excited though as it only has a low zenithal hourly rate. It’s a bit of an odd one in that the radiant is highest as darkness falls, giving higher meteor rates in the evening.

Moon declination reaches minimum on Friday so EME moon windows are short. Add this to high losses and this is a week for EME system maintenance and improvement. The Sun’s declination is falling giving a maximum sun elevation of 35 degrees this week, so now is the time for sun/cold sky measurements before it’s too low to clear ground noise.