RSGB
April 29, 2016
It’s been another mixed week, with
coronal holes dominating once again. The K-index, a measure of the disturbance
to the Earth’s magnetic field due to incoming solar plasma, fluctuated all week,
being as low as one and as high as four.
The solar flux index started the week at
82, but rose steadily to reach 94 by Friday. By then there were actually six
sunspot regions visible on the sun, although some were so small they looked like
dust on the lens.
Two small, but almost geo-effective,
coronal holes could be seen in the Solar Dynamics Observatory‘s extreme
ultra-violet image on Thursday, which suggest we may have unsettled conditions
as you hear or read this report. NOAA predicts the solar flux index could rise
to 95 by 3 May, although unsettled geomagnetic conditions will continue to
affect propagation, especially on the first and fourth.
As we are now in May, sporadic-E will
become prevalent on the higher HF bands, notably ten metres, but more about that
later.
Otherwise, a look at an HF propagation
coverage map from VOACAP Online shows May generally sees the start of the summer
doldrums when maximum usable frequencies are generally lower during daylight
hours, but remain higher at night.
VHF and up propagation news:
We may start this weekend with a weak
ridge of high pressure over southern Britain, which is potentially useful for
some limited tropo, especially down to the south towards western France and
northern Spain. Unfortunately, almost as soon as it happens, it will be gone and
low pressure will be in control, so it’s more likely to be rain scatter on the
GHz bands from large shower clouds that gives any enhancement locally.
On a more positive note, the sporadic-E
season is now under way and current weather patterns are producing good jet
streams in the right places over Europe. These are known to be helpful for
sporadic-E and the sporadic-E maximum usable frequency has already reached more
than 100MHz in the past week over the northern Balkans, and allowed UK stations
to have six metre QSOs with Greece.
Sporadic-E is not an everyday thing, so
check the beacons and clusters to follow any openings as it intensifies.
Openings usually start as short skip on 10m, then up through 6m to 4m and
perhaps even 2m. There are two main periods of activity from the UK, usually
late morning and again late afternoon into early evening.
Moon declination is climbing this week
and losses are falling as the moon comes in to perigee on Thursday. So this is a
good week for EME with a daytime moon.
