Propagation News – 20 July 2012

Solar activity retreated from the levels of recent weeks. Though C-class flares were reported on most days they had no marked impact on propagation. On the 16th and 17th no flares were reported and the solar disc was almost blank. The solar flux, which touched the 200 mark on the 8th, had declined to only 89 by the 17th. The average for the week, 118, was 59 units down on the previous week. The less volatile 90-day average, at 133, was three points down. The X-ray flux level was also down—from an average of C1.0 to B6.

However, happily for HF operators, the geomagnetic field was never more than slightly unsettled. The highest daily Ap reading was 9 and the average was 6. Solar wind speeds ranged between 288 km/sec on the 13th and 474km/sec on the 14th. Particle densities were consistently low and Bz varied around plus 5 and minus 4 nanoTeslas. HF propagation was at predicted levels but VHF Sporadic-E occurred only occasionally: the summer season is now clearly behind us—though there could still be brief openings.

Now the solar forecast. The low level of solar activity of recent days is expected to continue during the first part of the week, with few flares of consequence and generally quiet geomagnetic levels. However, by next weekend, the solar flux should be recovering some of the ground lost during the sharp decline of recent days. Daytime MUFs at equal latitudes are expected to be in the vicinity of 24MHz, while darkness lows will be about 14MHz. Paths to eastern North America should have a maximum usable frequency—that’s a 50 percent of a contact—around 23MHz. The Optimum Working Frequency, there should be a 90 percent chance of success, will be 17MHz.

Category: GB2RS Propagation News