Last week was characterised by solar flares – lots of them! There were numerous strong flares, although the majority occurred in the early hours and so didn’t affect the ionosphere over Europe. Solar flare events can cause short-lived radio blackouts as the energetic photons penetrate deep into the D-layer. Solar activity during the past 30 days has increased drastically with five of the top 10 strongest flares of Cycle 25 detected during this period alone.
We have also had very strong sunspot activity with the solar flux index peaking at 160 on Thursday the 21st. The current crop of four sunspot groups probably means we can expect the SFI to stay high until at least early next week.
NOAA predicts the SFI will stay above 130, but we may get even higher figures for a time. It also predicts a maximum Kp index of two next week, although that could easily rise if we get hit by matter from any incoming CMEs, which are getting more prevalent as the cycle continues. The good news is that, at the time of writing, it didn’t look like we will get any coronal hole activity.
There have been numerous reports of good conditions on the higher bands – 21, 24 and 28MHz – including openings to TX5N on the Austral islands. Braco, 8Q7DX, who is on holiday in the Maldives, has also been worked.
There have also been some signs of early Sporadic-E with very loud openings to Spain on 10 metres.
So if the SFI stays this high and we don’t get many geomagnetic disturbances it could be a good week for HF.
VHF and up:
We have a classic spring start to things with low pressure over the near continent, aided by the increasing warmth of the spring sunshine, while colder regions to the north become home to high pressure near Iceland.
Between the two, we will have a strong and cold-feeling east to northeasterly wind over the UK; not really the setup required for Tropo, since the strong winds and turbulence destroy any temperature inversion.
The changes come along after this weekend as the low weakens and a ridge of high pressure extends south across the country with much lighter winds and a chance of Tropo, especially overnight.
It is possible that isolated showers may offer a little rain scatter, but not a high probability.
It would be better to consider possible aurora and meteor scatter as your exotic modes. In this closing part of April, the best is within reach, since Sporadic-E is a serious possibility on 10m and perhaps 6m. Use the beacons and clusters to guide you, but if you start to adjust to your summer operating rule of checking for Es mid-morning and late afternoon or early evening, then Es QSOs will soon come.
The Winter minimum of meteor show activity is at an end with Sporadic meteor rates increasing towards their usual maximum in late summer.
The Lyrids shower has passed the peak, but continues to be active until the 30th.
Moon declination starts the week negative with low peak moon elevations and short visibility windows, but turns positive again on Thursday. Path losses are on the increase again as we are past perigee. 144 MHz sky noise is low all week except Saturday afternoon when the Sun and Moon are close in the sky for the five hours leading up to Moonset at approximately 1900hrs.
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