Propagation News 6 October 2013

All visible sunspot groups were either small or the larger groups were magnetically simple and as a result solar activity was very low. In total six small C class solar flares took place which increased activity to low on the 29th, 2nd and the 3rd. On the 29th one of these flares took place during a filament eruption and a large coronal mass ejection took place that headed our way. Solar flux levels increased from 103 units on the 29th to 114 by the 3rd averaged 107 units. The 90 day solar flux average on the 3rd was 110 units, that’s one unit down on last week. X-ray flux levels averaged B2.7 units and varied little day to day. Geomagnetic activity was very quiet until just after midnight on the 2nd when the coronal mass ejection that departed the Sun early on the 30th arrived and for the rest of the day a geomagnetic storm took place. Between 0300 and 0600 hours a Kp index of 7 took place during the most intense part of the disturbance. The Ap index for the 2nd was 43 units. The average was Ap 9 units. Solar wind data from the ACE spacecraft saw solar wind speeds decrease to a very slow 235 kilometres per second by the 30th. An increase in wind speeds from 380 to 640 kilometres per second took place in less than 30 minutes at the start of the disturbance. Densities were low except for an increase to 64 particles per cubic centimetre early on the 2nd. Bz varied between minus 1 and plus 2 nanoTeslas on the quiet days and between minus 29 and plus 24 nanoTeslas during the first half of the 2nd. The disturbance was not sufficiently severe for any but UK operators in northern Scotland to make auroral contacts. The HF bands are showing seasonal improvement with trans-Atlantic working up to 28MHz most days. However, on the morning of the 2nd MUFs were reduced by some 4MHz by the disturbance.

Finally, the solar forecast for the coming week. Yet again the coming week the prospects for solar activity increasing are very small. Solar activity is expected to be very low most days but could increase to low on the occasional day. Solar flux levels should be around the 100 mark for most of the week but could increase slightly towards next weekend. No coronal holes are expected and other than a coronal mass ejection then geomagnetic activity is expected to be quiet every day. MUFs during daylight hours at equal latitudes should be around 23MHz for the south and 20MHz for the north. Darkness hour lows are expected to be about 10MHz. Paths this week to South America should have a maximum usable frequency with a 50 per cent success rate of around 32MHz. The optimum working frequency with a 90 per cent success rate will be about 26MHz. The best time to try this path will be between 1300 and 1800 hours UTC.

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

Category: GB2RS Propagation News