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Propagation News – 11 November 2018

The large geomagnetic disturbance that we predicted last week actually hit the Earth on Sunday evening and Monday morning, as the plasma cloud was moving slower than experts predicted. Nevertheless, its effects were dramatic, pushing the Kp index to six and sparking widespread visible aurora, even from parts of the UK.

The geomagnetic storm hit HF conditions on Monday with showing maximum useable frequencies over a 3,000km path struggling to exceed 12 to 13MHz in the morning. Things did improve as the week went on, but conditions remained unsettled with the Kp index still hitting four on Thursday the 8th.

It would be good to be able to give you better news for next week, but another very large Earth-facing coronal hole on the Sun on Thursday means we can probably expect more unsettled geomagnetic conditions on Saturday the 10th and Sunday the 11th. NOAA agrees and predicts the Kp index could reach at least four, with the threat of suppressed maximum useable frequencies on HF. The better news is that conditions may then improve and we may see better HF propagation from Wednesday onwards.

There have been some HF highlights, however. Ron, G3SVW reports working Brian, 9J2BO in Zambia on 15 metres last Sunday, and Andy, M0NKR reports Andy, 5R8UP in Madagascar being active on 80m, which is a long haul from the UK for early November.

And now the VHF and up propagation news.

This weekend we are still under the influence of the large area of low pressure just to the northwest of Britain. This means a mild and rather breezy pattern of southwesterly winds and scattered showers, some likely to be heavy and perhaps thundery. Rain scatter will therefore be a possibility for stations on the microwave bands.

High pressure remains to the east of the UK and therefore Tropo will be only an occasional presence for the eastern side of the country, across the North Sea for example. This leaves us with the possibility of aurora due to disturbed geomagnetic conditions; the tip here is to follow the Kp index, which is a measure of how disturbed the Earth’s magnetic field is and thus indicates the prospects for aurora. Values greater than five or six should start to attract your interest.

As well as the smaller Northern Taurids meteor shower on Monday, the Leonids reach their peak next Saturday, and with a zenithal hourly rate, or ZHR, of 15 it’s one of the largest showers of the year. The Leonids occasionally produce a meteor storm with a ZHR of more than 1,000. The last one was 2001, but that’s not predicted this year. Look for enhanced reflections from today on the lower VHF bands.

The Moon is at minimum declination today and apogee on Wednesday so a poor week for EME.

And that’s all from the propagation team this week.

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