Propagation News – 9 October 2016

Last week the solar flux index didn’t behave as predicted and rose to 99 by Thursday. This was mainly due to the appearance of large sunspot groups 2598 and 2599. There were no major solar flares, only minor C-class events, but unsettled geomagnetic conditions continued thanks to ongoing coronal hole activity.

The K-index hit four and five earlier in the week, although conditions improved by Thursday. Next week looks to be quite settled, geomagnetically, with the SDO spacecraft’s extreme current ultraviolet image showing no Earth-facing coronal holes. NOAA predicts the highest K-index reading will be two early in the week, rising to four on Sunday the 16th. The US Air Force predicts the solar flux index should remain in the range 95-102. Sunspot group 2599 appears fairly settled, so we don’t expect any M or X-class solar flares.

If the forecast holds true it looks like HF conditions may be good next week. Maximum usable frequencies have been subdued, but if the settled conditions can continue we may expect openings up to 21MHz or higher at times. The best HF paths will still be north-south, but don’t ignore greyline contacts on 40 and 80 metres at dawn.

VHF and up propagation

There’s one strong message and one very weak message in the tropo forecast for next week. The strong message is that the high, which gave some fair tropo conditions in the last 144MHz UK activity contest, will decline after the weekend and gradually become displaced to the north of Scotland. At the same time, pressure will fall over southern Britain as it turns more showery and the north-easterly breeze picks up a little. So, not a good sign for tropo in the coming week.

The weaker part of the forecast message is that prediction models diverge as we head towards the end of the week. One version rebuilds the high from the north of Scotland to bring a renewed chance of tropo by the weekend, but other versions remain in the showery regime through to the end of the week and offer no potential return of tropo. As we are talking about 7-10 days ahead, uncertainty at this range is not unusual.

There are no meteor showers this week so keep looking in the early mornings for random contacts on the lower VHF bands. Moon declination increases this week, going positive on Friday, so EME moon windows lengthen. Losses are low and falling this week.

Category: GB2RS Propagation News