venerdì 6 settembre 2019

Propagation News – 8 September 2019

Our prediction last week that there would be a major geomagnetic storm turned out to be correct, although we got the timing a little wrong. The solar material from a coronal hole actually hit the Earth in the early hours of Saturday morning, rather than later that day, sending the three-hourly Kp index up to five. Such was its intensity that eventually the Kp index hit six. The solar wind speed exceeded 600 kilometres per second during the main event and auroras were reported around high northern and southern latitudes.

Some listeners reported a pre-auroral enhancement. Phil, GU0SUP found that 15m was alive late on Friday evening with South American stations on FT8. He also worked HK3GSO, ZS1DX and a few JAs on 30m. But by Saturday morning the HF bands were impacted and DX was a little harder to find. Next week NOAA predicts the solar flux index will remain around 67 or 68 as we continue into solar minimum.

After the potential for unsettled geomagnetic conditions at the beginning of the weekend, due to yet another coronal hole, things should then remain settled for the rest of the week. It seems that coronal hole activity will once again dominate forecasts for the time being.

VHF and up:
The pattern for the coming week offers high pressure as the predominant feature in the south of the UK, with a continuing chance of tropo to the south into France and Spain. The northern half of Britain will see areas of low pressure passing by the far north of Scotland, which will possibly bring some rain scatter at times and preclude any widespread prolonged tropo.

It’s probably the final curtain for sporadic E as we head into mid-September. There have been some very isolated openings on 10m, but 6m is getting very sparse now. Just remember that the data shows that it’s not a zero for sporadic E outside the main summer months, but it’s quite hard to predict. Best to use the many clusters available to make sure you don’t miss anything.

The end of this week sees the full Moon, known as the Harvest Moon, falling within 14 days of the autumn equinox. However, the week starts with relatively high sky noise on 144MHz of more than 1,000 kelvin. Path loss increases throughout the week as the Moon moves towards apogee. This would not be an ideal week for small station EME. On a brighter note, the full Moon next weekend occurs at low declination, which will favour those stations without elevation. The full Moon may, clouds permitting, allow a good visual sighting for beam alignment. For those lucky enough to run reasonable size antennas on the bands above 1GHz, there will be scope to work EME throughout the week.

There are no major meteor showers this week. The September Epsilon-Perseids minor shower is active from around 5 to 21 September, with a peak on the 10th. This shower is not expected to produce a large return, however. But it should be worth monitoring the usual meteor scatter frequencies on 6m and 2m as the unexpected might happen!