Propagation News – 31 August 2014

Solar activity increased to moderate levels on the 22nd and the 25th when low strength M class solar flares took place and to high levels on the 24th when a M5 class flare occurred. On the remaining days solar activity was low, with a total of 44 C class flares taking place. Since the 25th the sunspot groups responsible for these flares decayed and simplified magnetically. Solar flux levels peaked at 141 units on the 24th but then declined to 119 by the 28th. The average was 129 units. The 90 day solar flux average on the 28th was 128 units, that’s two units up on last week. X-ray flux levels increased to B5.9 units on the 24th before declining to B3.5 units by the 28th. The average was B4.8 units. Geomagnetic activity was quiet every day until the 27th and the 28th when a coronal mass ejection arrived that had departed the Sun from an event that took place on the 22nd. The Ap index for the 27th and the 28th was 21 and 25 units respectively. The average was Ap 10 units. Solar wind data from the ACE spacecraft saw solar wind speeds decline to a very slow 240 kilometres per second on the 26th but then increased 390 by the 28th. Particle densities were low except for the 27th, which increased to 20 particles per cubic centimetre. Bz varied between minus 3 and plus 4 nanoTeslas on the quietest day and between minus 15 and plus 6 nanoTeslas on the 27th, which was the most disturbed day. The magnetic disturbance resulted in auroral propagation from around midday on the 27th on 50, 70 and 144MHz through to the evening of 28th. However, this was a weak disturbance so only a handful of UK operators reported contacts.

Now the solar forecast for the coming week. This week the quiet side of the Sun is expected to be looking our way. Solar activity should be at low levels with only C class solar flares expected. Solar flux levels are expected to decline and be in the 110s for most of the week. Geomagnetic activity is expected to be at unsettled to active levels for the next couple of days due to a recurring coronal hole. Activity should then decline to quiet levels only to increase again next weekend. MUFs during daylight hours at equal latitudes should be around 24MHz. Darkness hour lows should be about 12MHz. Paths this week to India should have a maximum usable frequency with a 50 percent success rate of around 23MHz. The optimum working frequency with a 90 percent success rate will be about 17MHz. The best time to try this path will be between 1100 and 1700 hours UTC.

Category: GB2RS Propagation News