Propagation News
Solar data for the period from 18 to 24 April
Compiled by Neil Clarke, G0CAS
Solar activity was very low. No solar flares of any significance took
place at all. The solar flux declined slightly from 81 on the 18th to
77, then increased to 82 on the 24th. Interestingly, on that day the solar
disc became spotless. The 90-day solar flux average on the 24th was 89,
that’s four units down on last week. X-ray flux levels increased
from A1.5 units on the 21st to B1.1 by the 24th. This increase was in
response to a medium-sized sunspot group approaching the east limb a day
before rotating into view.
Geomagnetic activity was quiet, except on the 20th, which had an Ap index
of 21 units. This short-lived disturbance was due to a small recurring
coronal hole. The average was Ap 9 units. The Ace spacecraft saw solar
wind speeds increase from 330 kilometres per second to 600 by the 20th
and 23rd. Particle densities were low except on the 20th, when they increased
to 20 particles per cubic centimetre. Bz varied between minus 16 and plus
17 nanoTeslas on the 20th and between minus 4 and plus 8 nanoTeslas on
the quieter days.
HF propagation remained much as it has been in recent weeks. There were
few openings on 24 and 28 MHz but 14 and 18MHz provided reasonably reliable
propagation. All continents were workable on 14MHz at appropriate times
of the day. Last week's report noted that the summer Sporadic E season
should soon be under way. Sure enough, recent days have produced several
50MHz openings to south-east Europe, the Mediterranean and North Africa.
The solar forecast. The active side of the sun is expected to be looking
our way during the week of 1 to 7 May. Solar activity should be low. Over
recent weeks activity has been low at best, and this trend seems set to
continue. The solar flux should be in the 80s or 90s for most of the week.
Geomagnetic activity should start at ‘sub-storm’ levels due
to a recurring coronal hole but by midweek as the hole rotates out of
the way activity should decline to quiet levels. MUFs during daylight
hours at equal latitudes should be around 20MHz for the south and 17MHz
for the north. The darkness hour lows should be about 10MHz. These levels
quoted could be lower until midweek due to the coronal hole.
Paths this week to South America should have a maximum usable frequency,
with a 50 per cent success rate, of around 24MHz. The optimum working
frequency, with a 90 per cent success rate, should be around 19MHz. The
best time to try this path should be between 1600 and 2000UTC. However,
openings in that direction should start around midday but levels will
be slightly lower. Sporadic E could take place on the occasional day with
mornings or early evenings the most likely times to catch any openings.
The RSGB propagation news is also available in a Saturday update, posted
every Saturday evening and for more on propagation generally, see http://www.rsgb.org/society/psc.htm.
Source: GB2RS News - Courtesy of the
RSGB
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