Propagation News – 6 July 2014

| July 4, 2014

NASA’s twin STEREO spacecraft, which can see the far side of the Sun and make 3D images of incoming coronal mass ejections, have made my job of forecasting solar activity for GB2RS much easier. Later this year, the twin probes will pass directly behind the Sun and will have to be turned off. Operations could be curtailed for more than a year. The reason has to do with STEREO’s high gain antenna. Ironically, when the antenna points too close to the Sun, it overheats. As the probes pass behind the Sun, they can’t point their antennas at Earth without heat-sensitive components becoming dangerously hot. This engineering problem was not anticipated when STEREO was launched in 2006. However, it might be possible to avert a complete blackout using the antenna’s side-lobes. Tests in July will evaluate this possibility: let’s hope they are successful.

Several large sunspot regions returned to the solar disc during the period. These regions produced several major flares on their last rotation. Only one M class solar flare took pace, and this was on the 1st. Numerous C class solar flares took place every day, 58 in total. Solar flux levels increased from 104 units on the 27th to 178 by the 3rd. The average was 141 units. The 90 day solar flux average on the 3rd was 132 units, that’s one unit down on last week. X-ray flux levels increased from B4.6 to B9.6 units by the 1st. The average was B7.5 units. Several large coronal mass ejections took place but none headed our way. As a result the geomagnetic field was quiet every day and the average Ap index for the period was 6 units. Solar wind data from the ACE spacecraft saw solar wind speeds vary between 300 and 390 kilometres per second. Particle densities were low but increased to 26 and 28 particles per cubic centimetre on the 28th and the 29th respectively. With a quiet geomagnetic field, Bz showed only minor variations with fluctuations up to of minus 9 and plus 6 nanoTeslas. It was a good week for Sporadic-E, daily at up to 70MHz, and at times peaking to over 100MHz.

Finally, the solar forecast for the coming week. This week the active side of the Sun is expected to be looking our way. Solar activity is expected to be moderate on some days with also a small chance that activity could increase to high. Solar flux levels should be in the 170s for most of the week but levels could start to decline later in the week. Providing no coronal mass ejections head our way then geomagnetic activity is expected to be quiet every day except for the 11th, when a small recurring coronal hole could increase activity. MUFs during daylight hours at equal latitudes should be around 22MHz. Darkness hour lows should be about 14MHz. Paths this week to India should have a maximum usable frequency with a 50 per cent success rate will be around 21MHz. The optimum working frequency with a 90 per cent success rate will be about 16MHz. The best time to try this path will be between 1500 and 2000 hours. Sporadic-E is expected most days with openings up to 70MHz.

Category: GB2RS Propagation News

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