Propagation News – 17 September 2017

After the solar chaos of last weekend, things looked a little more settled at first. However, following last Sunday’s X8.2 solar flare, material from a coronal mass ejection impacted the Earth on Wednesday. The Solar Flux Index declined to 75 by Thursday, but we were seeing the geomagnetic effects of yet another coronal hole as this report was being written.

All this activity makes it hard to be precise about conditions next week, but NOAA predicts the solar flux index will be in the mid-80s, with unsettled geomagnetic conditions at times. Look for a low K-index over a couple of days for the best results on HF.

It is worth pointing out that a better indicator of real-time HF conditions can be the smoothed or averaged smoothed sunspot number, which is currently 17 or 22 according to which method is used. Smoothed numbers are used by VOACAP and G4FKH’s own predtest.uk prediction tool.

Propagation Studies Committee member Marcus, G0IJZ, reminds us that sunspot numbers and solar flux levels can be chaotic in the short term, but over the long term—that is, months—there is good correlation between the smoothed indices and ionospheric characteristics.

As we move into autumn, this can also be a good time to look for openings on the lower bands. Quite a lot of DX has been reported on 40m, especially around greyline times. The band is definitely worth checking.

VHF and up

Early last week we saw more of the predicted auroral propagation in the UK, so keep a check on the lower VHF bands in case the sun flares up again.

After a windswept and showery last week, there are signs that we start this weekend with the legacy of cool northwesterly winds and scattered showers, possibly thundery. This means continuing good rain scatter on the GHz bands from any of the heavier showers.

Last week, the weather models were hinting at high pressure building by this weekend, but it has been knocked back to early in the coming week. It’s still on the agenda for the southern half of the country and possibly the north at times.

By the end of the week, there should be a large high near southwest Britain. This could bring tropo into play for many areas by the time we get past mid-week and it looks good into the following weekend.

There are no meteor showers this week, so continue to look before dawn for the best random meteor scatter contacts.

Moon declination goes negative on Thursday and losses are climbing as the Moon moves away from us, so get your EME contacts in early this week for the best results.

Category: GB2RS Propagation News