RSGB
October 9, 2015
The
sun severely disrupted the HF bands again this week. A high-speed solar wind
stream with a south-facing Bz magnetic component continued to interact strongly
with the Earth’s geomagnetic field. Strong, G3 level geomagnetic storming was
observed at high latitudes and the K index hit seven on Wednesday evening. There
were long periods on Wednesday and Thursday where it sat stubbornly at five or
more.
The net result was a very depleted F2
ionospheric layer. At noon on Wednesday the critical frequency as measured by
the Chilton Ionosonde was just 3.7MHz, indicating a maximum usable frequency
over a 3,000km path of only 15MHz.
The only good news is that this means these
are good conditions to look for auroral propagation on the higher HF and VHF
bands.
Further storming may remain possible during
the next week due to ongoing coronal holes. Sky watchers should be alert for
visible aurora displays once it is dark.
With
the solar flux index at more than 130, if the geomagnetic storming decreases
there is a chance of decent DX if and when the F2 layer recovers.
The
autumn months of October and November are often a good time to expect Tropo
lifts due to the presence of areas of high pressure at this time of the year.
These can be slow moving and provide several days of enhanced conditions on VHF,
UHF and microwave bands.
The indications are that we may have a large
high over Scandinavia for most of the coming week, extending a ridge towards the
UK and down past Spain to the Azores. This could again bring lift conditions to
many parts of Britain, favouring E-W paths across the North Sea to southern
Scandinavia and the Baltic states, with a secondary option southwards past
western France to northwest Spain and the Canaries.
There
is a possibility that the North Sea paths may not quite last to the end of the
week though, as low pressure reaches northern Scandinavia by Friday. There are
no major meteor showers this week, so continue to look for the best random
meteor scatter QSO opportunities in the early mornings as the earth’s rotation
and orbital path combine to sweep up the maximum number of meteoric
particles.
The moon reaches apogee today and its
declination goes negative, meaning shorter, but daylight, Moon windows with high
losses in the coming week.
And that’s all from the propagation team for
this week.