Propagation – 19 May 2013

And now the solar factual data for the period from Friday the 10th to Thursday the 16th of May compiled by Neil Clarke, G0CAS on Friday the 17th of May.

With the aid of the STEREO Behind spacecraft that allows us to see sunspot regions many days before they are seen from earth, we saw a large flare producing active region was to rotate into view. This region came into view on the 13th and then in the next three days produced four X class solar flares. The largest was an X3 on the 14th, which was the third largest flare so far for this sunspot cycle. Several coronal mass ejections also took place but all were located at the east limb, which is not the ideal location for them to head our way, but a glancing blow is possible. Also, five M class and numerous C class solar flares took place. These X class solar flares are the first since last October. Solar flux levels increased sharply from 125 units on the 10th to 150 by the 13th, before a gradual decline to 145 units by the end of the period. The average was 143 units. The 90 day solar flux average on the 16th was 120, that’s three units up on last week. X-ray flux levels increased from B6.7 units on the 10th to peak at c1.1 units on the 13th. The average was B7.8 units, which is the highest level since the start of the year. Geomagnetic activity was quiet every day till the end of the period, when activity increased to unsettled levels with an Ap index of 15 units for the day. The average was Ap 7 units. Solar wind data from the ACE spacecraft saw solar wind speeds decline from 470 kilometres per second on the 10th to 320 by the 14th. Speeds then increased to 450 kilometres per second during the weak disturbance of the 16th. Particle densities were low except for the 15th and the 16th, which increased to 57 and 24 particles per cubic centimetre respectively. Bz varied between minus 4 and plus 3 nanoTeslas on the quiet days and between minus 9 and plus 11 nanoTeslas during the disturbance. The HF bands responded well to the higher solar flux levels and strong 70MHz Sporadic-E openings occurred on several days.

And finally the solar forecast for the coming week. This week solar activity could continue at high levels due to the current active sunspot region, which is still visible and also due to other active regions rotating into view that produced strong solar flares on their last rotation. Solar flux levels are expected to be around the 140’s or maybe slightly higher. Geomagnetic activity could be unsettled on Monday and Tuesday due to a recurring coronal hole. Also, a number of coronal mass ejections could deliver a glancing blow, which might increase activity on almost any day during the week. MUFs during daylight hours at equal latitudes should be around 24MHz for the south and 21MHz for the north. Darkness hour lows should be about 13MHz. Paths this week to South Africa should have a maximum usable frequency with a 50 per cent success rate of around or slightly higher than 30MHz. The optimum working frequency with a 90 per cent success rate of about 27MHz. The best time to try this path will between 1100 and 1600 hours. Sporadic-E is expected on some days with openings up to 70MHz.

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

Category: GB2RS Propagation News