Propagation News – 16 June 2024

| June 14, 2024

No sooner do we say that conditions will remain good than the Sun emits an X-class solar flare! Such is the challenge of writing propagation predictions.

Nevertheless, after the X1.5-class flare on the 10 June, things settled again and, at the moment, there are no incoming coronal mass ejections, or CMEs for short, to report. With a Kp index of less than 1 on Thursday 13 June, and a solar flux index of 165, it looks like HF conditions could be quite good.

However, the Sun’s proton flux has increased and is close to the 10 million electron volts warning threshold. This means that paths through the polar regions might be disrupted. Protons can herald the arrival of a CME two or three days later, although NOAA is not predicting any disruption.

On the 13 June, the critical frequency was between 7 and 8MHz, meaning a maximum useable frequency over a 3,000km path of around 21 to 24MHz. The 10m band will be open, mainly to Sporadic-E. However, F2-layer propagation on the 10m band will be sparse.

NOAA predicts the solar flux index will fall to around 155 today, the 16 June, before climbing again to around 195 in a week’s time. Geomagnetic conditions are predicted to be quiet all week, but that may be because solar flares and CMEs are hard to predict at this point in the solar cycle.

As always, make hay on the HF bands while the Sun shines! And make the most of the Sporadic-E propagation on the higher HF bands as June is probably a peak month for this.

Finally, the latest sunspot data show that the average sunspot number for May was 171.7, the highest in 22 years. However, the ARRL reports that shortwave conditions were above average on only six days out of the entire month of May, and mostly poor on half of the days due to geomagnetic disturbances and solar flares.

VHF and up

The current spell of seemingly endless, poor weather is struggling to provide much Tropo. The general theme is low pressure bringing active weather fronts with rain or, if not that, then scattered heavy showers.

This again points to rain scatter for the GHz Bands as the mode worth exploring. There is just one glimmer of Tropo hope in that the latest model predictions are starting to inject the notion of a ridge developing over southern areas, initially around mid-week but perhaps more so at the end of the week. Although, it’s fair to say that other models hang on to the low-pressure theme. That said, it’s worth checking from the middle of next week onwards.

There are no significant meteor showers this week so continue to check for random meteors around dawn.

The solar conditions have continued to trickle charge the auroral oval with an occasionally enhanced Kp index indicating possible aurora. This is unlikely to be visible at this time of the year although, if you are outside with a clear view to the north, you might be rewarded with a seasonal look at noctilucent clouds to make up for it.

High-summer Sporadic-E propagation is providing daily contacts so it’s worth checking the bands each day. The daily blogs always have something to show on the 10m band and on many days there are reports of contacts on the 6m band. Remember these openings are not always reachable from all parts of the UK. One of the characteristics of Sporadic-E is that at each end of the path the ‘signal footprint’ is very small. Even in a busy opening, signals may still pass you by but you should continue to monitor in case a Sporadic-E path opens up that does include your station at one end!

Moon declination is negative again from this weekend, ending today the 16 June. EME path loss was at its highest at apogee on Friday 14 June. 144MHz sky noise starts the week low but rises steadily, reaching over 3,000 Kelvin on Friday the 21 June.

Category: GB2RS Propagation News