Propagation News – 3 November 2019

Last week offered a mixed bag of HF propagation. The weekend saw the aftermath of a geomagnetic storm, triggered by matter from a solar coronal hole. This pushed the Kp index up to six and sparked auroras at the North and South poles. The disturbance eventually settled by Wednesday, after a few days of the Kp index hitting three. This didn’t stop top DXers working VP6R, the DXpedition on Pitcairn Island in the Pacific. A variety of modes were used to put the call sign in people’s logs, with the FT8 Fox and Hounds mode proving popular.

Next week we may see more of the same as the Sun continues to present zero sunspots. Geomagnetic conditions are a little harder to predict as a weak coronal hole stream is currently moving past Earth. Visible aurora will be likely at very high latitudes.

The US Air Force predicts the Ap index—and note, that’s not the Kp index—will remain at about five, with an increase to 10 on the sixth. This equates to a Kp index maximum of two, which suggests more settled conditions from this weekend onwards.

Daytime critical frequencies are struggling to get much above 6.3MHz at the moment, which translates to a maximum useable frequency over 3,000km of up to around 21MHz, and occasionally higher. There have even been reports of 28MHz openings. Night-time critical frequencies are currently around 3.25MHz, which doesn’t bode well for NVIS contacts around the UK on 80 metres. But longer distance contacts into Europe and further afield should still be possible at night.

VHF and up

The atmospheric forecast models are very good at predicting the general weather type out to some considerable time ahead. They seem to be in broad agreement about the coming period of weather being dominated by areas of low pressure and bands of rain or showers. This once again means that rain scatter will probably be the main weather-related propagation mode for next week.

High pressure is not really a candidate for tropo propagation modes next week and, since we are way past the main sporadic E season, the list scrolls down to the odd chance aurora and meteor scatter event. These are very hard to predict, other than recommending that you should be aware of any meteor showers and watch the various propagation bulletins that show the state of the solar wind and geomagnetic index.

Moon declination is increasing again from this Sunday, going positive this coming Saturday, meaning Moon windows will lengthen. The Moon is at apogee on Thursday so losses will be at their highest this week. 144MHz sky temperature reaches a minimum on Thursday.

There are no major meteor showers this week, but the big Leonids shower is just two weeks away, so get ready!

Category: GB2RS Propagation News