GB2RS News

And now the solar factual data for the period from the 23rd to the 29th of August, compiled by Neil Clarke, G0CAS on the 30th of August.

Solar activity was at very low levels for the week. No solar flares took place at all. The solar disc was spotless on the 23rd but on the 24th a large singe spot rotated into view. Solar flux levels declined slightly from 75 units on the 23rd to 72 by the 28th. The average was 74 units. The 90 day solar flux average on the 29th was at the same level as last week at 77 units. X-ray flux levels varied little day to day and averaged A6 units. Geomagnetic activity started at quiet levels on the 23rd with an Ap index of 5 units but overnight into the 24th a coronal hole disturbance arrived. The most disturbed day was the 25th with an Ap index of 20 units. Quiet conditions returned on the 29th with an Ap of only 2 units. The average was Ap 11 units. Solar wind data from the ACE spacecraft saw solar wind speeds increase from a slow 270 kilometres per second on the 23rd to a fast 710 by the next day. Speeds remained fast until the 29th when they declined to 430 by the end of the day. Particle densities increased to very high levels with 82 particles per cubic centimetre measured late on the 23rd. By the 26th particles had declined to 1 particle per cubic centimetre where they remained for the rest of the period. Bz during the disturbance fluctuated between minus 14 and plus 17 nanoTeslas and between minus and plus 2 nanoTeslas once the magnetic field had quietened down on the 29th.
And now the solar forecast. This week the slightly more active side of the Sun is expected to be looking our way. Solar activity though, will probably remain at very low levels but there may be a increased chance of activity increasing. Solar flux levels are expected to be in the low 80’s for most of the week. Geomagnetic activity should be mostly quiet everyday, saying that, the next couple of days could be slightly unsettled due to a small recurring coronal hole. MUFs during daylight hours at equal latitudes should be around 21MHz for the south and 18MHz for the north. Darkness hour lows are expected to be about 10MHz. Paths this week to the east coast of North America should have a maximum usable frequency with a 50 per cent success rate of around 20MHz. The optimum working frequency with a 90 per cent success rate will be about 15MHz. The best time to try this path will be between 1600 and 2100 hours. Every week these predications are for a quiet geomagnetic field, any increase in geomagnetic activity will decrease the MUF by several megaHertz, particularly on paths that go over or close to the polar regions. Paths over the equator to the southern hemisphere will be the least effected.
And that’s all for this week from the propagation team.

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/committees/psc.php

Also see the UK HF Propagation Prediction pages by Gwyn Williams, G4FKH