Solar activity was low throughout the week. C-class solar flares were reported every day, but there was only one smallish M-class flare. The solar flux began the period at 153 units, rose slightly, and then returned to 145, averaging 153. The 90-day average on the 27th stood at 159—two points up on the week. A coronal mass ejection occurred on the 23rd, with the effects reaching Earth on the 25th, but it struck only the lightest of glancing blows, scarcely showed up on the daily Ap figures, and had a negligible effect on propagation. Indeed the daily index reached double figures on just one day—the 21st, when it was 10. For the week as a whole the average was only a modest 6.5 units. The X-ray flux showed little variation day-to-day, averaging B6.2—a slight decline. Solar wind speeds reported by the ACE spacecraft ranged between 289km/sec on the 21st and 524km/sec on the 25th. Particle densities were generally low, apart for a spike to 10 particles per cubic centimetre on the 21st. Bz ranged between plus 7 and minus 5 nanoTeslas. Overall, low geomagnetic activity and relatively high solar flux levels made for consistently good conditions on the HF bands.
Finally, the forecast for the week ahead. Solar activity is expected to be low to moderate, with C-class flares on most days and the occasional M-class flare. A major X-class flare looks unlikely, as does any great increase in geomagnetic activity—though, as usual, the possibility of an Earth-directed coronal mass ejection cannot be dismissed. However, solar flux levels are expected to rise, possibly reaching the 170s. Aided by seasonal factors, MUFs at equal latitudes should again exceed 30MHz. Darkness lows are expected to be about 11MHz. Paths to India should have an MUF—that’s a 50 percent chance of a contact—of 34MHz. The optimum working frequency, at which there should be a 90 percent chance of success, will be 28MHz. The path should be best between 0900 and 1400UTC.
And that’s all for another week from the propagation team.
Category: GB2RS Propagation News