Last week was dominated by
extensive geomagnetic disturbances thanks to ongoing coronal hole activity on
the sun. Coronal holes are areas with open magnetic field lines that allow
plasma to escape as a high-speed stream. This plasma impacted the Earth causing
aurora and unsettled HF conditions, especially on paths over the poles.
The K-index was pushed
up to five and even six throughout the latter half of the week, bringing a mixed
bag of HF propagation.
At times the maximum usable
frequency was suppressed with noisy HF bands and very poor propagation. But
there were highlights, with enhanced HF propagation at times, up to and
including 21MHz. DX heard in the UK included D66D Comoros and S9BT Sao
Tome.
Next week NOAA predicts very
unsettled geomagnetic conditions for Sunday, 2 October and the first half of the
week and unsettled conditions for the remainder. The solar flux index will be in
the range 80-85, with a chance for C-class solar flare activity.
Because of the way HF conditions
can change quickly, we suggest keeping a close eye on the 20 to 15 metre bands
as short-lived openings may occur at any time during daylight hours. As we head
into October, DX is being worked and conditions will continue to improve.
VHF and up propagation:
The end of last week saw the
finish to very unsettled weather. This week, high pressure is due to build to
the east of Britain over Scandinavia and eventually link up with another area of
high pressure over Biscay. This should provide some modest tropo prospects at
times for many areas, although Ireland and western Scotland may remain too
breezy for any significant inversions to develop. The limiting factor of the
tropo may well prove to be fairly dry low-level air under the inversion, so the
better conditions will be seen when there is evidence of moisture near the
surface, like fog and mist.
Wednesday sees the Draconids
meteor shower. Don’t get too excited though as it only has a low zenithal hourly
rate. It’s a bit of an odd one in that the radiant is highest as darkness falls,
giving higher meteor rates in the evening.
Moon declination reaches minimum
on Friday so EME moon windows are short. Add this to high losses and this is a
week for EME system maintenance and improvement. The Sun’s declination is
falling giving a maximum sun elevation of 35 degrees this week, so now is the
time for sun/cold sky measurements before it’s too low to clear ground
noise.
http://rsgb.org/
