HF News
Last week’s solar conditions couldn’t get much better. We had a week of high solar flux indices, relatively calm geomagnetic conditions and, other than an X-class solar flare, not much else to report.
The solar flare originated from active region 3869 and reached a strong X3.3 in the early hours of October 24th. This event was associated with a coronal mass ejection (CME) based on solar dimming following the event, but because the flare location was located off the east limb, it was directed mostly away from Earth.
Once again, all the sunspots are in the southern hemisphere, but activity appears to be growing. This could spell trouble over the next week.
This weekend, the 26th and 27th, is the CQ Worldwide SSB contest and conditions should be excellent, with a combination of high solar flux and autumnal HF conditions.
Maximum usable frequencies are generally higher than 28MHz from dawn until dusk. Nightime MUFs over 3,000km are still just above 14MHz, although you might get better results by dropping down to 10MHz if 20 metres doesn’t work for you.
Next week, NOAA predicts that the SFI may rise again, perhaps hitting 185 as we enter November. However, this current bunch of sunspots rotating to be Earth-directed next week appear more active and we could see more solar flares and CMEs, which could throw a spanner in the works.
A solar flare could impact the ionosphere by increasing D-layer absorption, for up to an hour or so, and possibly launch a coronal mass ejection.
If a CME hits the Earth expect the MUF to plummet, at least for a day or two until the ionosphere recovers.
VHF and up
The Autumn Equinox period brought some amazing ionospheric propagation to 50MHz on Thursday last week with stations in the UK working morning paths to VK, JA, DS and XV among others.
Typically for 50MHz DX, the skip zones were sharp and moved rapidly. Stations even a few km apart experienced very different signals and paths. Those with a low noise floor had a huge advantage as signals were generally weak in the UK and only good for FT8, but some reports of a VK at +5 bucked this trend.
Next week will offer some reasonable Tropo conditions, although not without some occasional interrupts from weak frontal systems, especially in the far southwest and the far northwest of Britain. It’s not clear if these represent good rain scatter options, but they are more likely to temporarily curtail any Tropo for a while.
The solar conditions continue to feed the occasional aurora alert our way, so it’s always good to monitor the Kp index for signs of increasing above Kp=4. It won’t always go on to produce a radio aurora, but it's worth keeping an eye on things.
The meteor scatter prospects continue to be elevated by the decline of the Orionids, which peaked on Tuesday 22nd , and the Taurids, which are a very low-rate shower, but technically cover a broad period into December. The Leonids is the next major shower, but that doesn’t peak until mid-November.
Lastly, looking at the out-of-season Sporadic-E prospects, there are always days with minor enhancements of the critical frequency of the Es layer, as shown on the www.propquest.co.uk graphs. Certainly, there are stronger jet streams available in the autumn and winter, but other elements of Es are not so favourable. It’s usually a very marginal outcome at best, but nonetheless good enough for 10m or 6m and mostly for digital mode on FT8.
It could well be that trans-equatorial propagation or TEP is a more profitable venture.
For EME operators, Moon declination is positive, but falling, going negative on Tuesday the 29th. Path losses are rising, reaching a maximum at apogee on the morning of Wednesday the 30th. 144MHz sky noise is low until Friday 1st November when the Sun and Moon are close in the sky.
