Propagation News – 05 December 2021

The last week was characterised by unsettled geomagnetic conditions, but a reasonable solar flux index of 92, falling to 86. Despite NOAA predicting that the Kp index would be around two, we had an excursion up to five on Tuesday. This was due to an enhanced solar wind stream containing a sector of southward Bz, which kicked up a minor, G1-class geomagnetic storm. The southward direction of the interplanetary magnetic field meant that it could more easily couple with the Earth’s magnetic field, allowing solar plasma to flood it. This continued until the end of Wednesday, with the Kp index finally returning to one on Thursday morning.

Last weekend was the CQ Worldwide CW contest and HF conditions were aided by a very low Kp index. This was beneficial, especially for signals going over the pole. As a result, many stations were able to put the North Pole Contest Group, KL7RA, in Alaska, into their logs on 20 metres, where their signal was reasonably free of polar flutter.

Next week NOAA predicts that the solar flux index will start in the high 80s, but may tail off as the week progresses. Once again it predicts that the Kp index will be around two, but this is very dependent on there being no coronal mass ejections, which could add to the solar wind. A large coronal hole was Earth-facing on Thursday, which could possibly result in an elevated Kp index over the weekend and reduced maximum usable frequencies. Keep an eye on the website for details.

And finally, the darker and longer nights mean the low bands can start to come alive, so don’t ignore 160, 80 and 40 metres.

VHF and up

Testing times for antennas during this current spell of unsettled weather, which looks as though it will stay with us through all of the coming week. This means periods of wet and windy weather will bring a hint of rain scatter at times, but effectively rules out any tropo opportunities. Once again, it will be down to the slim chance of aurora and reliable random meteor scatter to liven up VHF operating.

The big Geminids meteor shower with a ZHR of 120+ is under way, but won’t hit its peak until the morning of the 14th of December. Predictions show a ZHR of 150 at peak, as ZHR has shown a slight increase over the last decades. It has reached 140 to 150 in recent years. The Geminids peak is broad, and close-to-peak rates persist for several hours. Expect several days of good meteor scatter activity in the days up to the 14th and expect it to decay fairly quickly after the maximum.

It’s an inconvenient period for EME enthusiasts, especially on the GHz bands, with the current phase of lowest path loss coinciding with lowest declination continuing. Perigee was last Friday, so path losses will increase as the week progresses. With Moon declination at minimum today, Moon windows will be short and it will not get above 15 degrees elevation until Wednesday. 144MHz sky temperatures are high during the early part of the week, and combined with the low elevation, VHF EME will be a noisy affair. In all, it’s looking like a very good week to try some satellite operation!

Category: GB2RS Propagation News