Propagation News – 10 May 2015

This last week has not been a good one for HF. On Sunday 3rd there were solar flares and an earth-facing coronal mass ejection, with further flares on Tuesday. Later on Tuesday evening there was a massive X-class solar flare that blocked out HF in the Pacific region. This was followed on Wednesday by a geomagnetic disturbance, with the Kp index hitting five. These combined to give poor HF conditions at times, despite the solar flux index rising to 136.

Looking ahead, large sunspot region 2339 was coming around the eastern limb of the sun at the time of writing. This was the region that brought the X-class flare, so we may be in for a rough ride next week.

The solar flux index is predicted to be in the range 140-150, but we can expect unsettled geomagnetic conditions, especially in the latter half of the week when the Kp index could hit five again. This may help depress maximum usable frequencies and generally disrupt long-range HF paths. The good news is that we are now in the Sporadic-E season, which may bring good short skip on the upper HF bands, especially 28MHz, but more of that later.

VHF and up propagation

Next week, expect fairly flat tropo conditions. There will be a weak ridge of high pressure close to southeast England at first, which may provide some slight enhancement to the near Continent, but it’s not expected to last long.

Last week we saw some Sporadic-E from the UK, but at the time of writing this was very marginal. It’s widely accepted that weather events play a role in determining some of the locational properties of Sporadic-E. To keep up to date with possible weather triggers for Sporadic-E, the RSGB Forum discussion group contains a section called Radio Propagation Questions. In there you will find the threads, Jet Stream Weather Charts For Es Research —Chart Drawer, containing daily postings of jet stream weather charts plus commentary, and Jet Stream Weather Charts For Es Research – Discussion for your feedback and questions. These charts may help you to look in the right directions for the DX. It’s not a forecast of Sporadic-E, but a new tool to encourage further research and discussion, so feedback is welcomed.

Category: GB2RS Propagation News