Last week was characterised by low
sunspot activity, but very unsettled geomagnetic conditions. The solar flux
index was in the mid to high 70s, but the K index was five or six for days on
end, and even peaked at seven. This was high enough for automatic visible aurora
e-mail warnings to be sent out by Lancaster University.
The noon Chilton Digisonde plot
from Harwell suggested that only 20 metres would be open, with the higher bands
closed. These poor conditions were caused by a massive coronal hole on the sun.
This hole is recurring and brought the same conditions 27 days ago. Rest
assured, we can probably expect a repeat performance again around November
22nd.
With regards to LF/MF propagation,
the Dst index was depressed to -80nT on the 25th but is rising slowly. It would
seem from reports that LF/MF propagation on paths over 2,000km has suffered but
not as much as might be expected. It seems that though the solar wind velocity
had increased, the plasma density is low. This suggests there may be lower
levels of electron precipitation and a faster recovery of conditions than would
be expected after a coronal mass ejection.
Next week looks set to continue
with the poor geomagnetic conditions. NOAA suggests the K index will remain at
around five until a much-needed respite beginning around the 2nd of
November.
VHF and up propagation news:
Most of this week will be dominated
by high pressure and this is likely to continue to provide slightly-enhanced
Tropo opportunities for many areas although, like last week, the better
conditions will be when there is moist air near the surface, which quite often
means those typical foggy autumnal nights and mornings.
The longer range models do,
unfortunately, suggest that the high weakens and is replaced by low pressure in
the second half of the week, so it won’t last forever.
As for operating tips, it’s simple;
don’t restrict yourself to FM and repeaters, and do remember to try the other
modes on VHF/UHF because SSB and CW can produce surprising results – and there’s
plenty of spectrum space down there.
For meteor scatter enthusiasts, we
are now approaching the peak of the Taurids meteor shower, a diffuse shower that
lasts from late September until late November. Don’t get too excited though, as
the meteor rate is low. It does though, have a reputation for some fireballs.
Look for a peak overnight around the 4th and 5th of November.
The Moon is close to the Sun today
so noise will be high, especially on the low bands with wider antenna
beamwidths. Combined with a low declination and high losses at apogee on Monday,
it’s a week for EME system maintenance only.
