via the RSGB: 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.