Propagation News – 9 October 2022

Yet another good week for HF propagation has passed, although it has been borderline in terms of geomagnetic disturbances.

The Kp index hovered around the four mark all week, mainly due to high-speed streams from the solar wind, possibly from slight glancing blows from incoming CME material. There have been a few M-class solar flares, but nothing too violent. The risk of X-class flares though remains relatively high.

The solar flux continued to climb despite pessimistic predictions, ending up at 161 and a sunspot number of 151 on Thursday.

Daytime critical frequencies have been in the range of 7.5 – 8MHz, meaning 40m has been an excellent inter-G band during the day. MUFs over a 3,000km path have been exceeding 24.9MHz, and occasionally 28MHz, especially in the early afternoon.

This has meant that HF propagation has been good with excellent openings on all the upper HF bands. Paul, GM4ULS has even reported hearing what we believe to be round-the-world echoes while listening to high-power European stations on 20m calling for long-path Asia, VK and ZL contacts in the morning.

This is a sure sign that the ionosphere is playing ball!

Next week the US Air Force predicts that the solar flux will remain in the 150s to start with but may then decline into the 130s as the week progresses. The Kp index is predicted to be no more than three all week, although an incoming CME could soon spoil that.

Coronal hole activity appears to be minimal, once we get past the effects of a small hole on the equator, which became Earth-facing on Wednesday. This could result in the Kp index rising on Friday, although the hole’s size means the effects may be short-lived and perhaps minimal.

So, in conclusion, it is Autumn with an SFI in the 150s and an active, but not unsettled, geomagnetic field. In other words, it should be good for HF DX unless a solar flare or CME comes along and spoils things.

VHF and up

The typical Autumn weather will continue over the next week, meaning alternating ridges of high pressure between active weather fronts with rain and strong winds.

There have been some reasonably uplifted Tropo conditions during recent spells of high pressure and no reason to think this won’t be the case over the next week. The two most likely high-pressure transitions across the country are this weekend and again in the first half of next week. Paths to the south into the continent should do well.

In between these events, we find active weather fronts crossing the country with a large low taking up residence by the end of the week. This could lead to a few rain scatter options for GHz bands, but Autumn storms can be fast-moving and hard to track.

The Sun continues to offer support with a high Kp index on occasions so always a chance of aurora.

The Draconids and the Orionids are the major meteor showers this month. The former, peaking today, Sunday, with a typical ZHR of 10, has been known to reach storm level. The Orionids is active from the 2 October to the 7 November peaking on the 21 October with a medium ZHR of 20.

Random meteor scatter propagation is always available and rates are high in October, so it’s always a banker if you have a decent system for the low VHF bands.

With all these more exotic modes the best course of action is to monitor the clusters for signs of activity.

Moon declination goes positive today (Sunday), so Moon windows will lengthen as the week progresses. We are past perigee so path losses will increase throughout the week. 144MHz sky noise is low all week.

Category: GB2RS Propagation News