Propagation News 11 August 2013

| August 9, 2013

Numerous small sunspot regions were visible every day but all were quiet and most were in gradual decay. Solar activity was very low, with no C class solar flares taking place at all. This is the first week with no C class solar flares since the last solar minimum. Solar flux levels declined slightly from 113 units on the 2nd to 104 by the 5th. The average was 106 units. The 90 day solar flux average on the 8th was 116, that’s two units down on last week. X-ray flux levels varied little day to day and averaged B2.5 units. Geomagnetic activity started at quiet levels but by the 4th and the 5th increased slightly to unsettled levels due to a recurring coronal hole. The Ap index for the 4th and the 5th was 18 and 17 units respectively. Activity on the remaining days decreased to quiet levels and the average was Ap 9 units. Solar wind data from the ACE spacecraft saw solar wind speeds increase from 290 kilometres per second on the 3rd to 610 by the 5th. Speeds then gradually declined to 360 kilometres per second by the end of the period. Particle densities were low except for a brief increase to 72 particles per cubic centimetre on the 4th. Bz varied between minus 13 and plus 7 nanoTeslas during the disturbance and between minus and plus 3 nanoTeslas on the quietest day. Sporadic-E reached 70MHz on some days.

And finally the solar forecast for the coming week. Currently, the Sun is very quiet with no major solar flares having taken place for numerous weeks. There are no positive signs that solar activity is going to increase to any levels higher than low. When activity does increase it will be with very little warning. The coming week solar activity is expected to be at very low to low levels with only C class solar flares taking place. Solar flux levels are expected to be around 110 units. Geomagnetic activity is expected to start at quiet levels but around midweek a small recurring coronal hole is expected to increase geomagnetic activity slightly. Quiet levels should return to quiet by next weekend. 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 South America should have a maximum usable frequency with a 50 per cent success rate of around 28MHz. The optimum working frequency with a 90 per cent success rate will be about 22MHz. The best time to try this path will be between 1400 and 1900 hours UTC. Sporadic-E should take place on the lower VHF bands some days. Also, between the 11th and the 13th the Perseids meteor shower will peak.

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

Category: GB2RS Propagation News

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