HF News

Last week saw a mixed bag in terms of HF propagation with good conditions at times, but horrendous conditions mid week after a coronal mass ejection saw the Kp index shoot up to six.

Matter from the CME, which was accompanied by an M1.6 solar flare on October 9, hit the Earth in the early hours of October 12.

A geomagnetic storm then ensued and widespread visible aurora were reported at high latitudes.

On Tuesday MUFs were affected adversely with maxima over a 3,000km path down from 28MHz to less than 14MHz at times during the day.

By Thursday, and with the Kp index back down to between zero and two, signals had recovered to near normal levels, with a maximum daytime critical frequency of 7.125MHz being recorded on the Chilton Digisonde, which equates to more than 27MHz over a 3,000km path.

This does go to show that we can expect more CMEs, and poorer conditions at times, as we head towards solar maximum in a few years time.

Next week NOAA predicts the solar flux index will be in the range 85-90 with a maximum Kp index of four on the 19th.

So make the most of the Autumnal HF conditions and work as high in frequency as you can to minimise D-layer absorption.

VHF and up

The coming week’s weather will change to mixed and unsettled, with little chance of Tropo propagation, caused by periods of rain, showers and strong winds. At best we can hope for some rain scatter activity.

The exact time when these changes of type occur in our weather patterns is one of the hardest for the models to get right, but at the moment most suggest Sunday night into Monday.

Since the autumn is typically a good season for auroras, perhaps some warbling auroral notes will return again after last week when plenty of auroral QSOs were reported on 144 MHz. Sadly for the UK, they were almost exclusively for the more northerly Nordic countries. A few northern UK stations, namely G4KUX, MI0XXZ and GM4VVX reported a few auroral CW QSOs on the 12th.

The 21st sees the peak of the Orionids meteor shower with a ZHR of 15. Orionids are pieces of Comet 1P/Halley, famously known as Halley's comet. Add this to two small meteor showers, the Epsilon Geminids with a ZHR of three peaking on the 18th, and the Leonis Minoris with a ZHR of two peaking on the 24th, next week should be good for meteor scatter enthusiasts.

Moon declination goes positive again on Monday so we’ll see the Moon reaching higher elevations at its zenith. Path losses are still increasing as we are past perigee.

A seasonal reminder from the team to do your end of summer check on those antenna ropes and fixings before we see too many windy days.