Propagation – 26 May 2013

And now the solar factual data for the period from Friday the 17th to Thursday the 23rd of May, compiled by Neil Clarke, G0CAS on Friday the 24th of May.

Numerous sunspot groups were visible every day, some were large and magnetically complex to produce sizeable solar flares. Solar activity varied between low and high. Three M class solar flares took place, one on the 17th, 20th and the largest on the 22nd. All produced sudden ionospheric disturbances and coronal mass ejections. Solar flux levels started the period at 136 units but declined to 125 by the 21st. The average was 133 units. The 90 day solar flux average on the 23rd was 122 units, that’s two units up on last week. X-ray flux levels increased from B4.8 units on the 18th to C1 by the 22nd. The average was B6.6 units. Geomagnetic activity started at unsettled levels with an Ap index of 24 units on the 18th and 14 the next day. Activity then declined to quiet levels for the remainder of the period. The average was Ap 12 units. Solar wind data from the ACE spacecraft saw a gradual increase in solar wind speeds from 360 kilometres per second on the 17th to 500 by the 22nd. Particle densities were moderate most days with 30 particles per cubic centimetre recorded on the 18th. Bz varied between minus and plus 4 nanoTeslas on the quietest day and between minus 13 and plus 9 nanoTeslas on the most disturbed day. Sporadic-E occurred most days on 28, 50 and 70MHz. An experimental propagation beacon, WG2XPN, is currently beaming to Europe with a 3 kilowatt ERP from grid square FM67 on 70.005MHz, to explore possible trans-Atlantic propagation on 4m during the summer sporadic-E season.

And finally the solar forecast for the coming week. This week the quiet side of the Sun is expected to be rotating into view. Solar activity is expected to be at low levels, however, activity could increase to moderate levels on some days. Geomagnetic activity should start the week at quiet levels but from midweek onwards activity is expected to increase due to a recurring coronal hole. MUFs during daylight hours at equal latitudes should be around 23MHz for the south and 20MHz for the north. Darkness hour lows should be about 13MHz. Paths this week to Japan should have a maximum usable frequency with a 50 per cent success rate of 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 1000 and 1500 hours UTC. MUFs will decline during any magnetic disturbance, especially high latitude and polar paths. Sporadic-E is expected to take most days on 28MHz and the lower VHF bands but only occasionally on 144MHz.

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

Category: GB2RS Propagation News