Propagation News – 21 September 2014

| September 19, 2014

Solar activity was high at the beginning of the week, but more settled towards the end. There were numerous M class flares during the week. Conditions rose to moderate levels as sunspot region 2157 produced an M class flare on the 14th. The 90 day solar flux average on the 18th was 131, that’s up one on last week.

Geomagnetic activity was generally setted everyday, except for the 12th, which was the most disturbed day with an Ap index of 44 units. The cause of this disturbance was a solar flare and associated coronal mass ejection stemming from an M4.5 eruption on September 9th. The average was Ap 14 units. Solar wind data from the ACE spacecraft saw solar wind speeds peak at around 600 to 800 kilometres per second, although the rest of week was more settled with speeds dropping to 400 to 600 kilometres per second. Once again, the Bz was most volatile around the 13th with large fluctuations. It was mainly neutral for the rest of the week.

Now the solar forecast for the coming week. This week two active sunspot regions, which have already rotated into view, will become more earth facing. Solar activity is expected to be low to moderate on most days. Solar flux levels are expected to remain at similar levels, with a solar flux index in the 130-150 range. Geomagnetic activity is expected to be quiet most days, with continuing risks of M-class solar flares. An Earth-directed coronal mass ejection at some stage in the next week cannot be ruled out. We are now at the autumnal equinox and can expect conditions on the upper HF bands to continue to improve. This time of year favours north-south paths, such as UK to South Africa or South America. The Optimum Working Frequency during daylight hours on these paths is expected to be 24 or 28MHz. The best time to try the path to South Africa is between noon and 1800 hours UTC. The South American path has a peak around noon and then again at about 1700-1800 hours UTC. Darkness hour lows on these paths will be either 10MHz or 14MHz.

Category: GB2RS Propagation News