Propagation News – 11 September 2016

| September 9, 2016

Last weekend saw very unsettled geomagnetic conditions due a large coronal hole across the sun’s equator. This impacted SSB Field Day, with the K-index being pushed as high as four and five, sparking visible auroras at high latitudes and depressed maximum usable frequencies. The solar flux index hung tantalisingly close to 100 during the week, but couldn’t quite make it.

The good news is that better autumnal conditions are beginning to show, with the noon daytime critical frequency as measured by the Chilton ionosonde exceeding 5.6MHz on Wednesday. This indicated a maximum useable frequency of up to 21MHz on longer paths. There have also been some late season sporadic E openings on 10 metres, giving weak but useable short 28MHz skip to the south of France and Spain.

Next week the USAF predicts the solar flux index will start at around 90, decline slightly, and then peak at more than 100 next weekend. The extreme ultraviolet image from the SDO spacecraft on Thursday showed no Earth-facing coronal holes, so fingers crossed we may have more settled conditions this week. NOAA, however, does predict a K-index of four for Tuesday the 13th.

Mid-September often marks the start of better HF conditions, so if you have been put off over the last few months, now may be the time to switch on the radio.

VHF and up propagation

We had some very good tropo including a GM to EA8 contact last week and we start the coming week in a similar vein, after a brief cooling off period. It seems that, although high pressure will be nearby over the continent for the start of the week, the unsettled weather over Scotland and Ireland will edge south-east as the days pass. Even so, there may still be high pressure near to southern areas and over Biscay to offer paths towards Spain and Portugal for stations in the west.

Heading into autumn we usually hit the key time for overnight and early morning mist and fog. These conditions are perfect for tropo, so make use of the visual clues and you’ll get some more new squares into the log.

The Moon is at minimum declination tomorrow so EME Moon windows will start to lengthen and losses will fall to minimum at perigee on the 18th.

The Orionids meteor shower continues with no large peak into November, so continue to look out for enhanced meteor scatter conditions this coming week.

Category: GB2RS Propagation News