Propagation – 5 May 2013

| May 3, 2013

Now the solar report for the period from Friday 26 April to Thursday the 2nd of May, compiled by Martin Harrison, G3USF, on Friday 3rd May.

Solar activity was mostly low, though numerous C-class flares were reported every day. The level rose to moderate on the 2nd, when an M1.9 flare was reported. The solar flux increased from 122 on the 26th to 165 on the 30th, the highest level since January. The average over the week was 144, which is 33 higher than the previous week. The 90-day average gained 3 points to 115. The X-ray flux was also up, from an average B4.5 units to B7.9. Geomagnetic activity was variable. A C7 flare on the 24th resulted in a short, sharp disturbance early on the 26th and an Ap index for the day of 18 units. HF MUFs were depressed by a couple of MHz for most of the day. During the next few days geomagnetic activity was low, with the Ap index in single figures. There was another disturbance on May 1st. A high-speed coronal stream caused a minor storm when the interplanetary magnetic field turned south to -11 nanoTeslas. Particle densities, which were generally low, surged to 43 per cubic centimetre. The Ap index for the day was 21. VHF aurora was reported from midday through to the evening. As usual, its main UK beneficiaries were in Scotland. However, just before that disturbance, the whole UK had strong Sporadic-E at both 50 and 70MHz, and the MUF was reported to have reached 87MHz.

Now the forecast. Solar activity is likely to remain mostly low. However, several sunspot groups now on the solar disc or about to turn into view have the potential for M-class flares. The solar flux may fall back from the level of recent days, possibly into the 130s. The geomagnetic field is expected to be mostly quiet, though a recurring coronal hole may lead to slightly higher levels at the start of the week. The major uncertainty is whether one of the sunspot regions facing us will produce a coronal mass ejection, bringing a disturbance later in the week. MUFs at equal latitudes will be around 23MHz in the south and 20MHz in the north. Darkness lows will again be about 12MHz. Sporadic-E up to 70MHz should occur on most days. It is still a little early in the season for openings on 144MHz, but they have been known. So it’s a good idea to keep an ear on Band 2 FM for rising MUFs. Paths to South America this week should have a maximum usable frequency, with a 50 per cent chance of a contact of 28MHz. The optimum working frequency, where there should be a 90 per cent prospect of success, will be 22MHz. The best times will be between 1300 and 2100UTC.

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

Category: GB2RS Propagation News

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