Propagation News – 20 November 2022

The good HF conditions continued last week with a low Kp index and a reasonable solar flux. But is that all about to change?

The problem is a large coronal hole in the Sun’s southern hemisphere, which became geoeffective on Thursday. The hole is at mid-latitude, so is not completely in line with Earth. But its large size means that we could see a strong solar wind, which may hit the Earth this weekend, potentially pushing the Kp index up for a couple of days at least.

Sunspots have been adequate rather than outstanding. The main active groups have now rotated out of view, but there are some new ones just appearing over the Sun’s limb.

The HF bands have been excellent and many newer amateurs have had their first taste of 10m in full flow.

Next week NOAA predicts that the solar flux index could decline to the range 105-115. The Kp index is predicted to rise to four at least until the 22 November. We may then get respite for a day or two before it rises again to three or four.

In other words, we have probably seen the best of the settled HF conditions for a while. Just what effect the enhanced solar wind and increased Kp index this weekend will have on maximum usable frequencies is hard to predict.

Typically, an increased Kp index can result in reduced MUFs, but whether we will see it impact 10 metres, especially with the predicted lower SFI, we will just have to wait and see.

 VHF and up

After last weekend’s excellent tropo, with 24GHz propagation from the South East of England to the near continent, we now have a seemingly never-ending period of unsettled weather continuing through the coming week.

This is driven by a strong jet stream flow across the Atlantic. Since it’s a low pressure and rain scatter period once again, it’s worth a reminder that, although we are way out of season with regards to Sporadic-E, it can still be seen on the foEs graphs on the website and can be particularly useful for the LF bands.

Focusing back on VHF and above, the prevalence of low pressure during the week suggests Tropo is unlikely to entertain us. The only modes remaining to discuss are meteor scatter as we slowly fade from the peak of the Leonids, and finally the prospect of a random aurora if we have further disturbed solar conditions.

This week’s active meteor showers are the Alpha Monocerotids which are active until November 25 and reach a low ZHR maximum on Monday the 21 November. Also, the November Orionids, which are active until 6 December but don’t peak until the 28 December.

Moon declination went negative on Saturday so Moon windows will shorten and zenith angles decrease. Path losses are still low but with perigee on Friday, path losses will fall all week. 144MHz sky noise slowly increases, reaching a maximum of over 2,500 Kelvin on Friday.

Category: GB2RS Propagation News