Propagation News – 23 June 2024

| June 21, 2024

We had a relatively quiet week, with the Sun generally being settled. There were coronal mass ejections, but they were on the far side of the Sun and not Earth-directed.

There were no X-class flares, although we did have a few C- and M-class events.

The solar flux index declined to 167 but has since recovered and stood at 196 on Thursday the 20 June. Active regions 3712, 3713 and 3716 are all large and 3712 has been emitting flares. However, all three regions will soon rotate out of view, so should not be a threat in the coming week.

As such, HF conditions have been reasonable given the time of year. Maximum usable frequencies over a 3,000km path during daylight have generally been between 14 and 21MHz, although there have been occasional openings up to 24MHz. Sporadic-E remains the main propagation mode on the 10m band.

Next week NOAA predicts that the solar flux index will remain in the 175 to 190 range and geomagnetic conditions are predicted to be mainly settled.

However, the far-side coronal mass ejections we have been seeing suggest we could be in for a rough ride in about a week to ten days. So, this week could be a good time for HF propagation.

VHF and up

The weather is trying to change to a more summer-like pattern, which means that the main jet stream will be farther north than recently and this will make Sporadic-E harder to find than during the recent strong jet stream pattern over Europe.

For most UK stations, the emphasis for Sporadic-E paths will gradually shift from the typical central Europe and Mediterranean to perhaps Scandinavia and the Baltic states.

The relatively new player this time around will be high pressure which comes and goes during the period but should bring some useful Tropo. In these high-summer days, sea or coastal paths are often good, but paths across hot land do not fare well in summer during the daytime. Concentrate on the night or early morning, especially if foggy.

There will be occasions when small lows and fronts edge into the south and west of the British Isles and, in typical summer fashion, may bring a risk of thundery showers. Any local, heavy rain means good conditions for rain scatter on the GHz bands. Meteor scatter again remains in the random category, which usually peaks around the dawn period.

Lastly, a note about aurora which has been kept at arm’s length although there have been several periods with a slightly enhanced Kp index. The light summer nights mean that visible auroras are very unlikely but do look out for noctilucent clouds on the northern horizon around midnight.

Noctilucent clouds are thin, wispy clouds that glow with a blue or silvery hue at night when illuminated by sunlight from below the horizon.

The Moon is at minimum declination this coming weekend so peak elevation is low and windows of usage are short. EME path loss is falling as we approach perigee next Thursday the 27th. 144MHz sky noise is high this weekend but falls to low early next week.

Category: GB2RS Propagation News