Propagation – 21 April 2013

| April 19, 2013

And now the solar factual data for the period from Friday the 12th to the 18th of April compiled by Neil Clarke, G0CAS on Friday the 19th of April.

Solar activity started at moderate levels when a M3 class solar flare took place during the evening of the 12th. Since then activity was low with only occasional C class solar flares taking place. However, none occurred on the 14th and solar activity was at very low levels. Solar flux levels declined from 138 units on the 12th to 105 by the 18th. The average was 117 units. The 90 day solar flux average on the 18th was 111 units, that’s two units down on last week. X-Ray flux levels declined from B5.9 units to B2.8 units by the 17th and the 18th. The average was B3.5 units. Geomagnetic activity was quiet every day. The most disturbed day was the 14th, with an Ap index of 10 units. The average was Ap 5 units. Solar wind data from the ACE spacecraft saw solar wind speeds decline from 550 kilometres per second to end of the period at 280 kilometres per second. Particle densities were low except for the morning of the 14th, which increased to 20 particles per cubic centimetre. Bz varied between minus 5 and plus 6 nanoTeslas except for the 14th, which varied between minus 8 and plus 12 nanoTeslas.

And finally the solar forecast for the coming week. At least for the first half of the week the quiet side of the Sun will be in view. However, after midweek the more active side of the Sun will start to rotate into view. Solar activity is expected to be very low on the occasional day but should increase later in the week. Solar flux levels are expected to be around the 100 mark but should increase to around 110 units by the end of the week. Geomagnetic activity is expected to start at quiet levels but by midweek increase due to two recurring coronal holes. There are two holes, one in each hemisphere with the hole in the southern hemisphere the larger. Activity should have declined to quiet levels by the end of the period. MUFs during daylight hours at equal latitudes should be around 23MHz for the south and 20MHz for the north. Levels could be slightly lower during any geomagnetic disturbance. Darkness hour lows should be around 12MHz. Paths this week to the Middle East should have a maximum usable frequency with a 50 per cent success rate of around 23MHz. The optimum working frequency with a 90 per cent success rate will be about 18MHz. The best time to try this path will be between 0900 and 1600 hours UTC. Normally, around the end of April sees the start of the summer Sporadic-E season. It will still be some weeks yet before openings become frequent and reach the VHF bands.

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

Category: GB2RS Propagation News

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