Solar activity was slightly higher this week. C-Class flares were reported daily and a couple of M-class flares occurred on the 1st. However, there were no Earth-directed coronal mass ejections. The solar flux started the week at 168 and ended at 137, averaging 144, compared with134 the previous week. The 90-day average was stable at 130. The X-ray flux increased from B4.3 to B6.3, with little daily variation. Geomagnetic activity was also higher, with unsettled periods on several days. The high point was the 4th, when the Ap index rose to 12. The daily average was 7.6, compared with 6.3 the previous week. Solar wind speeds recorded by the ACE spacecraft were above average for much of the week, thanks to a high-speed coronal stream. They were initially 285km/sec but climbed to 463km/sec on the 4th, remaining above average for the remainder of the period. The increase in geomagnetic levels had little impact on HF propagation but led to periods of radio aurora at VHF at high latitudes on several days. Bz varied between plus and minus 5 nanoTeslas during quiet periods and plus or minus 9 nanoTeslas at more unsettled times. Particle densities were low.
Now the solar forecast. There are currently no signs of change in the broad pattern of recent weeks, though, as ever, an Earth-directed coronal mass ejection could just surprise us. No great variation is expected in solar flux levels. Flare activity will mainly be low, but isolated M-class flares are possible. Geomagnetic levels should stay low, with the Ap index mainly in single figures. MUFs at equal latitudes are expected to reach about 24MHz. Darkness lows will be in the vicinity of 14MHz. Paths to southern Africa should have a maximum usable frequency, with a 50% chance of success, of 32MHz. The optimum working frequency, with a 90 per cent prospect of a contact, will be about 24MHz. The path should be in good shape between 0800 and 1800UTC.
Finally, a reminder that one of the year’s major meteor showers, the Perseids, which have been with us since 26 July, are scheduled to peak between now and 13 August.
And that’s all from the propagation team for another week.
Category: GB2RS Propagation News