Propagation News – 2 April 2023

We were right in our prediction about the effects of the large solar coronal hole last week, which saw the Kp index peak at 7.67 with widespread aurora visible from the UK, even in the south.

This was probably the most significant geomagnetic event we have had so far in this solar cycle.

Last week saw another X1.2 solar flare erupt on the Sun. This one erupted from active region 3256 on the 29 March at 0233UTC. It didn’t impact the ionosphere over the UK, but a fadeout was observed over the Pacific region.

This was the seventh major solar flare since 2023 began. The Sun has now matched 2022’s total –and it’s only March!

The associated CME off the southwestern limb of the Sun was modelled and determined to be well ahead of the Earth’s orbit. This means that we are unlikely to see the Kp index rise as a result of this event.

This region also produced an M1.2 flare that peaked around 1407UTC, and an M1.1 flare at 2347UTC. The earlier flare didn’t seem to affect the ionosphere too much according to the ionosonde data.

A minor solar wind stream is heading for Earth and is due on Saturday 1 April. The material is flowing from a relatively small coronal hole in the Sun’s atmosphere, but it is on the equator and very Earth-centric. Expect Arctic auroras and an elevated Kp index when the solar wind arrives this weekend.

The SFI remained fairly static, around 160, earlier in the week but then declined to 148 on Thursday 30 March. NOAA predicts that this decline will continue next week, perhaps down to the low 130s. Once the weekend’s geomagnetic conditions recover, NOAA predicts that the rest of the week should be quite settled.

This is good news for HF propagation, although do continue to watch out for solar flare and CME activity which could affect conditions and MUFs.

VHF and up

We have three phases of weather to consider over the next week. Forecasts predicted an unsettled weekend with rain and strong winds, so should have provided a focus for rain scatter on the GHz bands.

The weekend ends with developing high pressure which lasts into early next week. There is good potential for some tropo from Sunday afternoon until about Tuesday lunchtime.

At the time of writing, the best paths are likely to be from southern England into the near continent, also via Biscay to northern Spain and across the southern North Sea to Denmark.

The third phase occurs when the high moves to the south to allow fronts to move in from the Atlantic across northern Britain, but possibly still leaving tropo into France and across Biscay. Later in the week, the high pressure may head back north again to reintroduce tropo to northern areas.

The Sporadic-E season is fast approaching, typically from mid-April on 10m. If anything does happen before then, check the propquest.co.uk website for the Es blog tab, which shows the current day’s jet streams and will maybe provide a clue for which direction to beam.

Remember to look for aurora if the Kp index reaches five or more and, of course, meteor scatter around dawn for those random meteor QSOs.

For EME operators, Moon declination is positive until Wednesday, so still plenty of Moon time to get some QSOs in. Perigee was last Thursday, so path losses are now falling. 144MHz sky noise is low, rising slowly throughout the week

Category: GB2RS Propagation News