Propagation News – 25 August 2013

| August 23, 2013

Up to ten sunspot regions were visible during the period. Some were large and magnetically complex but solar activity remained at low levels except for the 17th when activity increased to moderate levels when the only M class solar flare took place. In total, 25 C class solar flares took place. Solar flux levels increased from 120 units on the 16th to 132 by the 20th. The average was 128 units. The 90 day solar flux average on the 22nd was 113, that’s one unit down on last week. X-ray flux levels increased gradually from B3.6 units on the 16th to B5.9 by the 22nd. The average was B4.7 units. Two recurring coronal hole disturbances took place during the period. The first was on the 16th, with an Ap index of 28 units, and the second was on the 21st with an Ap of 20 units. Quiet conditions took place between the two disturbances with an Ap of only 4 units on the 20th for example. The average was Ap 12 units. Solar wind data from the ACE spacecraft saw solar wind speeds decline from 860 kilometres per second during the 16th to 370 by the 20th. However, speeds increased to 610 kilometres per second with the arrival of the second disturbance. Particle densities were low except for an increase to 25 and 22 particles per cubic centimetre on the 20th and the 21st respectively. Bz varied minus 9 and plus 8 nanoTeslas during the 16th and between minus 10 and plus 7 nanoTeslas during the 21st. On the quieter days fluctuations of between minus and plus 3 nanoTeslas took place.

And, finally, the solar forecast for the coming week. This week the quiet side of the Sun is expected to be looking our way. Solar activity is expected to be at low levels almost every day. Solar flux levels should decline and be around 110 units later in the week. Geomagnetic activity is expected to be at quiet levels until next weekend when a recurring coronal hole is expected to increase activity. MUFs during daylight hours at equal latitudes should be around 23MHz for the south and 20MHz for the north. Darkness hour lows should be about 12MHz. Paths this week to South Africa should have a maximum usable frequency with a 50 per cent success rate of around 30MHz. The optimum working frequency with a 90 per cent success rate will be about 25MHz. The best time to try this path will be between 1100 and 1500 hours UTC. The end of August normally sees the end of the summer Sporadic-E season in the northern hemisphere, this year will be no different. Occasional openings are possible until the end of October. They can happen at any time and are impossible to forecast. However, a reliable short winter season takes place around Christmas and the New Year period.

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

Category: GB2RS Propagation News

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