Propagation News 15 December 2013

| December 13, 2013

The number of sunspot groups increased from 5 on the 7th and the 8th to 10 by the 10th. Most were small and simple but a couple were much larger. However, solar activity was only at low levels except for the 7th which increased to moderate levels when the only M class solar flare took place. Solar flux levels increased from 151 units on the 6th to 175 by the 9th. The average was 165 units. The 90 day solar flux average on the 12th was 135 units, that’s seven units up on last week. X-ray flux levels declined from C1 units on the 6th to B7.3 units by the 11th. The average was B8.7 units. Geomagnetic activity was quiet every day except for the 8th when activity increased due to a coronal hole disturbance. The disturbance was strong but short lived. The Ap index on the 8th was 17 units and the average for the period was 4 units. Solar wind data from the ACE spacecraft saw solar wind speeds increase from 320 kilometres per second on the 6th to 690 by the 8th. Speeds then declined once the disturbance was over to 270 kilometres per second by the 12th. Particle densities were low except for the 7th and the 8th, which increased to 34 and 30 particles per cubic centimetre respectively. On the quiet days Bz varied between minus 2 and plus 1 nanoTeslas and between minus 24 and plus 20 nanoTeslas on the most disturbed day. HF band conditions were very good most days. Another high pressure system produced excellent propagation on the VHF and UHF bands up to 10GHz. All in all a good week.

Finally, the solar forecast for the coming week. This week solar activity is expected to be mostly low but there is a good chance that activity could increase to moderate levels on some days. Solar flux levels are expected to be around the 160s at first but may decline during the week. Geomagnetic activity is expected to be quiet every day provided no coronal mass ejections head our way. MUFs during daylight hours at equal latitudes should be around 33MHz, maybe slightly lower for the north. Darkness hour lows should be about 8MHz. Paths this week to Japan should have a maximum usable frequency with a 50 per cent success rate of around 26MHz. The optimum working frequency with a 90 per cent success rate will be about 20MHz. The best time to try this path will be around 0800 hours. A small but reliable winter Sporadic-E season takes place during the second half of December and lasts into the first half of January.

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

Category: GB2RS Propagation News

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