Propagation News – 30 June 2024

We had another lucky week with quite a high solar flux index, low Kp geomagnetic numbers, few solar flares and no coronal mass ejections, or CMEs, of note. In fact, you couldn’t ask for better!

But is that all about to change? With nine active solar regions on the Sun’s surface and the return of old region 3664, now renamed 3723, it would be a brave person to suggest otherwise.

So, let’s take a closer look at the Sun. Of the nine active regions that are visible, four are classed as stable, one is classed as declining and four are classed as growing.

With a solar flux index of 181, there is plenty of UV radiation around. However, we are currently in the summer doldrums so maximum useable frequencies, or MUFs, are lower than they are in the Autumn and Winter. In other words, we are not going to see a return to reliable worldwide DX conditions on the higher bands until mid to late September.

There is currently only a 5% chance of a strong X-class solar flare, although a bright coronal mass ejection was observed for a second day off the Sun’s west limb. This was directed away from our planet so shouldn’t affect us.

NOAA predicts that the Kp index could rise due to CME arrivals from an event that left the Sun on the 24 June. Expect a Kp of 4 or 5, with a reduction in the MUF until the geomagnetic disruption abates. It also predicts that the solar flux index will remain in the region of 190, hopefully with a low Kp index after the ionosphere settles again.

MUFs over a 3,000km path are generally between 18 and 23MHz during daylight and around 18MHz at night. This means that for the next month or so we may expect 14MHz to remain open throughout the night.

VHF and up

The current week finishes with a return to unsettled weather and cooler air, after a brief taste of summer, particularly in the south of Britain.

There will be lows drifting in from the Atlantic during the coming week, as well as the occasional passing weather front. Although there was some Tropo last week, during the brief period of high pressure, this is unlikely to be repeated in the coming week.

Therefore, we have a continuing random chance of some rain scatter, but you will need one of the many online weather radar displays to track the scatter regions down. Since next week also looks windier, you might have to keep one hand on the rotator!

Meteor scatter is once again down to random events, which means an early start in the shack to capture the higher rates in the early mornings.

The solar conditions continue to keep trying to creep into VHF affairs with a higher Kp index and thoughts of radio aurora, but it’s probably not a strong shout.

Now to our last item – Sporadic-E. There is still the broad summer Sporadic-E peak, which extends into the first week of September in a good year, so you have plenty of time. It will not always be there but, in a test analysis of Dourbes data in June 2022, 84% of the days reached 10m, with 18% up to 6m and around 10% to 4m or above. This makes it worth using the 10m band to highlight the regions of activity and then check the 6m beacons in case it strengthens to bring in the higher bands.

Moon declination goes positive again this coming weekend so Moon peak elevation and window lengths will increase. Perigee was on Thursday 27 June so EME path losses are increasing again. 144MHz sky noise is low at the start of the coming week and moderate later. From Friday afternoon on the 5 July to midday on Saturday, the Moon and the Sun are very close in the sky, meaning high noise for all but the narrowest beamwidth antennas.

Category: GB2RS Propagation News