Propagation News – 14 July 2013

| July 12, 2013

Several sunspot groups were visible at first but this declined to just two by the 10th. These two groups were large and magnetically complex but despite that no M or X class solar flares took place. In fact, only a small number of C class solar flares took place. As the two groups decayed and simplified so the solar flux levels declined from 141 units on the 5th to 113 by the 11th. The average was 124 units. The 90 day solar flux average on the 11th was 121 units, that’s one unit down on last week. X-ray flux levels declined from B7.9 units on the 5th to B3.5 by the 9th. The average was B4.6 units. During the period two geomagnetic disturbances took place. The first on the 6th was due to a slow moving coronal mass ejection and the Ap index for the day was 32 units. The second was due to a small recurring coronal hole and the Ap for the 10th was 30 units and 25 on the 11th. The average was Ap 19 units. Solar wind data from the ACE spacecraft saw solar wind speeds decline from 380 to 290 kilometres per second by the 7th but then increase to 490 kilometres per second on the 10th during the coronal hole disturbance. Particle densities were low except for the 5th and the 9th when 32 and 29 particles per cubic centimetre were recorded respectively. Bz varied between minus 13 and zero nanoTeslas on the 6th and between minus 12 and plus 6 nanoTeslas during the 10th. VHF aurora was report for many hours on the 6th, the 10th and the 11th, however, only a few contacts were made from the U.K.

And finally the solar forecast for the coming week. This week the quieter side of the Sun is expected to rotate into view. Solar activity is expected to be mostly low with only a small chance of activity increasing any higher. Solar flux levels are expected to be slightly above the 100 mark at first but then show a slight increase towards next weekend. Geomagnetic activity is expected to start at quiet levels but around midweek activity is expected to increase due to a recurring coronal hole. MUFs during daylight hours at equal latitudes should be around 22MHz for the south and 19MHz for the north. Darkness hour lows should be about 14MHz. Paths this week to Japan should have a maximum usable frequency with a 50 per cent success rate of around 18MHz. The optimum working frequency with a 90 per cent success rate will be about 14MHz. The best time to try this path will be between 0800 and midday UTC. Sporadic-E is expected to take place most days but openings on 144MHz will become less frequent but not totally ruled out.

Category: GB2RS Propagation News

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