HF News
Last week’s aurora may have come as a bit of a surprise! The propagation segment for GB2RS is usually written on a Thursday, but the aurora was sparked by a solar flare that took place two days later, at 20:02 UTC on August 30.
As we don’t have a crystal ball we couldn’t have predicted it!
The Kp index hit six late on the 1st, with aurora visible over a lot of the UK. HF was affected with sudden swings in the MUF over most of the day on Tuesday 2nd September.
At the time of writing a geomagnetic storm watch remains in effect with the solar wind speed above 500km/s. September is a good month for aurora due to the Russell-McPherron effect, when the Earth’s axis aligns perpendicularly to the Sun-Earth line during the equinox. This creates ideal conditions for a reconnection between the solar wind and Earth’s magnetic field. So keep an eye on solarham.com for daily updates.
The Sun remains active with plenty of sunspots. The solar flux stood at 187 on Thursday 3rd, down from 202 the day before.
HF propagation remains good (out of the auroral periods) and as we progress into September it should improve even more. Top DX this week has been VK2/SP9FIH on Lord Howe Island using Superfox FT8, and T30TTT on Western Kiribati, using both CW and FT8. Other choice DX included 3C3W (Equatorial Guinea), again on FT8, TJ1GD (Cameroon) on 20m CW and 5H8HZ (Tanzania) on 30m FT8.
Next week NOAA predicts the solar flux index will decline to 160, and then perhaps 125. Unsettled geomagnetic conditions are forecast for September 7th to the 10th with a maximum Kp index of four predicted. This may be due to a large elongated coronal hole on the Sun’s surface, which became Earth-facing on Thursday 3rd.
VHF and up
The return of unsettled weather takes a brief pause over the Newark Rally days ready for rain and sequences of low pressure to drive the weather agenda for much of the coming week.
The only reasonable chance of Tropo appears to be Friday and Saturday with high pressure to the southeast and support for paths to the continent and across the North Sea. Worth noting that, in general, short-lived highs like this one do not have the necessary time to generate a strong elevated inversion before declining, so don’t expect too much.
Rain scatter, on the other hand, is much more likely to be worth considering for the GHz stations next week with plenty of rain events coming along.
The sporadic-E season daily blogs have now finished for this year, but you may still find it worthwhile looking at the Dourbes graph on www.propquest.co.uk and you will notice the odd blip on the foEs trace, so keep it in mind for 10m and 6m, at least for the next week.
Meteor scatter is still in the random territory for this period between the Perseids in mid-August and Draconids, which peak on October 8th. So that means the pre-dawn morning hours will be good times to try.
There were some auroral signals during the 2m UKAC contest last Tuesday evening, September 2nd, and we are coming into the autumn season, when conditions, along with spring, tend to be more favourable for aurora.
The message is, of course, to monitor the Kp index for values rising above about Kp=4-5. Remember these three-hourly planetary readings can smooth out shorter duration peaks, so maybe don’t wait for it to get to the dizzy heights of Kp=6 or 7 before taking an interest.
Moon declination is still negative, not going positive until Monday 8th. So Moon window lengths and peak elevation will continue to increase. Path losses are still falling until perigee on Wednesday the 10th. 144MHz sky noise is low all week.