Propagation News – 21 July 2013

| July 19, 2013

Several sunspot groups were visible every day with most quiet and stable. However, two were medium sized and magnetically complex but these could only produce a couple of small strength C class solar flares each day. In total 16 C class solar flares took place. Solar flux levels gradually declined from 118 units on the 12th to 111 by the 17th. The average was 114 units. The 90 day solar flux average remained the same level as last week at 121 units. X-ray flux levels showed little variation day to day and averaged B3.8 units. Geomagnetic activity started the period at unsettled levels and then increased to sub-storm levels by the 15th with an Ap index of 35 units. The disturbance was probably due initially to a small coronal hole and then a coronal mass ejection. The average was Ap 16 units. Solar wind data from the ACE spacecraft saw solar wind speeds decrease from 560 kilometres per second on the 12th to 330 by midday of the 17th. Particle densities were moderate most days with a high of 22 particles per cubic centimetre during the 15th. Bz varied between a maximum of minus 10 and plus 3 nanoTeslas during the disturbance and between minus and plus 4 nanoTeslas on the quietest day. Radio aurorae took place from midday of the 14th till the afternoon on the 15th, but only a few contacts were reported from the UK. Sporadic-E propagation occurred every day, up to 70MHz.

And finally the solar forecast for the coming week. This week the quiet side of the Sun is expected to be looking our way. Therefore, solar activity is expected to be only at low levels with only C class solar flares taking place. Solar flux levels should be around 120 units at first but by the middle of the week a decline could take place. Due to a recurring coronal hole geomagnetic activity is expected to increase for most of the week. Activity could decline to quiet levels by next weekend. MUFs during daylight hours at equal latitudes should be around 21MHz for the south and 18MHz for the south. Darkness hour lows should be about 13MHz. Paths this week to the east coast of North America should have a maximum usable frequency with a 50 per cent success rate of around 17MHz. The optimum working frequency with a 90 per cent success rate will be about 13MHz. The best time to try this path will be between 1700 and 2200 hours UTC. Sporadic-E is expected to take place on some days.

Category: GB2RS Propagation News

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