Propagation News – 21 August 2022

| August 19, 2022

It looks like the Sun continued to be unsettled with an enhanced solar wind from coronal holes making itself felt here on Earth. A geomagnetic storm pushed the Kp index to six for two consecutive six hour slots on the evening of the 17th, although it was fairly quick to recover. However, it wasn’t long before the Kp index was up to five again on Thursday afternoon.

Meanwhile, the solar flux index climbed, peaking at 131, but then declining to 123 by Thursday.

The first geomagnetic storm affected the ionosphere with critical frequencies dropping to just over 5MHz. This meant that DX was mainly closed to frequencies above 14MHz. The storm on Thursday, the 18th, saw an initial enhancement with MUFs over a 3,000km path hitting 21MHz.

We have had a run of geomagnetic storms, which is par for the course as we ramp up with solar cycle 25. The bad news is that this is likely to continue. It does however mean that aurora watchers and auroral radio operators will get more opportunities as the year moves on.

NOAA predicts that the solar flux index will decline to the high 90s after starting the week at around 100. It does predict relatively settled geomagnetic conditions, but as we have said before this is likely to change at short notice thanks to solar flares, and their associated coronal mass ejections, plus the effects of coronal holes.

We may have seen the best of sporadic E this season, although there may be weak openings on 10 metres that are best captured via FT8 and other JT digital modes.

VHF and up

It’s a changeover to rather unsettled weather with Atlantic systems bringing some occasional bands of rain or showers across the country and the possibility of some rain scatter on the GHz bands.

Later in the coming week, there are hints that a new high will build in from the Atlantic to bring a return of some tropo conditions. This may leave conditions a bit flat on VHF until after midweek or a bit beyond, so it could be worth seeking out any late-season sporadic E activity in the meantime.

Although Es have been rare lately, you might still find some glimmers of hope into the first week of September. In such fleeting events you will often find the digital modes can flag up a potential direction to explore, starting on 10m and then migrating up to 6m as an event develops.

The solar activity has recently brought some auroral conditions, so remember to keep an eye on the Kp index in case further auroras materialise. As well as using the traditional 10m or 6m and occasionally 2m bands for this, you will often get a strong indication from even 80m signals sounding ‘hollow and watery’ and that is a cue to check for VHF aurora.

Meteor scatter is always a go-to mode if all else fails, especially in the early mornings when random meteors are at a peak.

With high Moon declination this week we have long Moon windows, but with apogee on Tuesday, path losses are at their highest for the lunar month. 144MHz sky noise is moderate and falling but be aware that the Sun and Moon are close to eclipse next Saturday morning meaning high Sun noise for a while.

Category: GB2RS Propagation News