Solar Minimum and Radio

Yesterday morning, always interested to learn what G0KYA's blog has to say about things radio, I clicked on his Blogger site to find an article about solar minimum and propagation.

Much to his credit, G0KYA has allowed my lighthearted critique of an argument that:

'we can expect the minimum to be around late 2019 or 2020. It is hard to be precise, as the minimum is something you can define after the event, not before or during!' 

When I commented that 12m has been very strong to the point of regular, almost daily and very long-haul DX, G0KYA came back with:


'Yes, but we are not at sunspot minimum yet and won't be for a couple of years. This was looking ahead to 2019/2020. The recent DX has also been helped by ionospheric enhancements from the coronal holes and is not sunspot related.'

It's a decent comment, but does fall down flat on its face when measured against the earlier comment that 'it is hard to be precise' about the solar cycle length.  Even harder (though in favour of G0KYA's viewpoint), when the solar activity is reducing, and cycle lengths (probably) increasing.

Then there is the fact that the depth of solar minima varies quite a bit.  Like the financial markets, historical data does not necessarily provide a reliable indicator of the future. 

Like maxima, minima vary in profundity and duration.  Image: NASA.

Is it reasonable to pin our radio hopes (or despair!) on a minimum not happening for the next two or so years?  It depends on what you term 'solar minimum', for a start.

To me (a first in Astronomy and Planetary Sciences, former Fellow of the Royal Astronomical Society (they pay their bosses too much for my liking!)) and most scientists, solar minimum is a period within a solar cycle, not a discrete, single point.  

So discussions that try to dance around some hallowed future day (or month), where we can raise our hands to the sky and shout 'we are at MINIMUM!' is simply misguided.  In fact, you can never know in real time and with that degree of accuracy.

We could be at solar minimum now.  In a late 2014 web release discussing then new research, NASA asserted:

'This research paper forecasts that the sun will enter solar minimum somewhere in the last half of 2017, with the sunspots of the next cycle appearing near the end of 2019.'

That prediction seems to have been pretty good in terms of predicting an earlier than G0KYA's minimum forecast.  But it may have been way off on cycle 25's commencement, because in January 2017, the Royal Observatory of Belgium announced that the first sunspot of solar cycle 25 had been identified.  A video shows some more detail.

That doesn't necessarily mean that the solar minimum period is over, of course, precisely because it is a period, not a single point.  The Sun is a chaotic mass of endless layers of swirling plasma.  It doesn't run like a machine with fixed cogs.  That's what makes it very hard to predict.

Here's how the plot of 10.7cm radio flux is going right now.  You can see that there has been, for a near-minimum point, an unusually pronounced spike in activity recently.  That, of course, will probably come back down to the trend line shortly.  It may even collapse to a new low for the cycle.  Or it may begin a new, upward trend.  We don't know and can't know with our current state of knowledge.

From the solar physics point of view, it's clear that the Sun is already within a minimum period of its sunspot cycle.  Whether or not it has reached, on average, the very lowest point is something that we can never know until at least 6 months after it has happened, because it relies on smoothed data gathered over that length of time.  Even then, there are periods within the low that are higher than weeks or months previously.

But there are unambiguous signs that the Sun is beginning to wipe away the sleep from its eyes.

From the radio operator's perspective, the effects of a solar minimum are already evident.  Prediction software and printed propagation guides in the magazines are very pessimistic (PredTest seems to be a bit less so of late), especially about the higher bands.  For example, according to RadCom, I can expect a couple of hours or so of very poor propagation no further than Europe at 12m for November 2017.

But does this pessimism mean that the higher bands aren't worth bothering with?  When I bought my Yagi for 12m in 2013, It cost about £230.  A year later, clearly anticipating poor propagation and thus low antenna sales for that band, the maker was selling it for half that price.  

This might well have been a mistake, because my log for 2017 is full, almost every day, of very good 12m DX contacts on digital modes.  FT8 has brought an upswing in higher band use as well, I would say.  YB0, 3B, JA is as good as it gets.  Most propagation predictions for 12m are way, way off.  As off as you can be, in fact.


Sometimes, as G0KYA points out, this good propagation is due to coronal hole effects.  But that's certainly not the whole story.  Indeed, the experience of operating 12m in October 2017 is very much like operating when the solar cycle was at or near its peak: in essence, signals come from the direction of the Sun, and you have a nice day tracking DX west (from the UK) across the globe until just after sunset.  If you extend the current activity point back across the past cycle, you get equivalent activity for early 2011 and 2016 - both periods where the log is chock-full of higher-band activity.

As most wise radio men will say: if you call out, you will  probably get a reply.  This sounds silly, and that you can't fight ionospheric physics.  But if you don't call - if everyone doesn't call - then you will certainly not get a reply!

It's a consistent feature of 12m that as soon as a QSO is made and reported to the cluster on that band, within a minute or two, the band will be full of callers.  There is a very strong herd mentality in the radio community, reinforced by the herding effects of web clusters.

Whilst I respect the people who try to predict propagation, I've never found it an area that is worth bothering with.  It is, in the end, a binary phenomenon: you switch on your radio and call CQ.  There either is propagation (and someone has been optimistic enough to listen), or there isn't. But it is always, always, worth calling and listening.

Oh, and just o underline the message, here's what happened during 90 minutes of WSPR on 10m at 1W this (22/10/17) afternoon, using a vertical delta loop cut for 20m:a 2-way exchange with Reunion!