Propagation News

| October 14, 2012

And now the solar factual data for the period from Friday the 5th to Thursday the 11th of October, compiled by Neil Clarke G0CAS on Friday the 12th of October.

Several sunspot groups rotated into view during the period and, in doing so, produced a number of M class solar flares on the 8th, 9th and the 10th. Associated with some of these solar flares were coronal mass ejections, but none were heading our way. Numerous C class solar flares took place from the 7th. Solar flux levels declined at first to 98 units on the 7th but increased to 117 units by the 11th with the appearance of the sunspot regions. The average was 106 units. The 90 day solar flux average on the 11th was 118 units, that’s five units down on last week. X-ray flux levels increased from B1.7 units on the 6th to B5 by the 11th, the average was B3.3 units. Geomagnetic activity started at quiet levels, with an Ap index of 4 units on the 5th, but by the morning of 8th activity increased and lasted till the afternoon of the 9th. The Ap index on the 8th and the 9th was 40 and 50 units respectively. The disturbance was the combination of a coronal mass ejection that departed the Sun on the 5th and a coronal hole. The average was Ap 17 units. Solar wind data from the ACE spacecraft saw solar wind speeds increase from 290 kilometres per second on the 6th to 560 by early on the 10th. Particle densities increased to 45 particles per cubic centimetre on the 8th, otherwise densities were low. Bz varied between minus 5 and plus 4 nanoTeslas on the quiet days and between minus 16 and plus 12 nanoTeslas on the 8th and 9th. During the geomagnetic disturbance HF propagation was considerably degraded, particularly on the east-west paths, but substantially recovered by the 11th. There were many reports of auroral propagation on 50 and 144MHz but relatively few UK operators appear to have benefited.

And finally the solar forecast for the coming week. This week the more active side of the Sun is looking our way. Solar activity could be at moderate levels on some days. There is a slight chance that activity could increase to high with an X class solar flare taking place. Solar flux levels should increase and could be as high as 130 units. Geomagnetic activity should be quiet today but a slight increase could take place for the next couple of days due to a recurring coronal hole. Also, an Earth directed coronal mass ejection could also increase activity, particularly later in the week. MUFs during daylight hours at equal latitudes are expected to be about 29MHz for the south and 26MHz for the north. Darkness hour lows should be around 9MHz. Paths this week to Australia should have a maximum usable frequency with a 50 per cent success rate of about 30MHz. The optimum working frequency with a 90 per cent success rate will be around 24MHz. The best time to try this path will be between 0800and 1200 UTC.

And that’s all for this week from the propagation team.

Category: GB2RS Propagation News

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