Thursday, 23 July 2015

Is this the end of Solar Cycle 24?

Is this the end of Solar Cycle 24? No.

But it is clear that the graph points downwards when it comes to solar activity.

These graphs come from the US NOAA, featured on SolarHam, and feature their measurement for the Solar Flux and the Sunspot Numbers:-

You can see that they predict that we are on the down slope of the curve, which was smaller than last cycle. A trend towards lower peaks has been noticed for several cycles now.

We tend to home in on the smoothed graph, but things go up and down a lot. We can hope for a few spikes upwards for quite some time yet.

As  I write (23 July 2015), the solar flux index is 89 and the sun spot number is 35. The two numbers are related, so I tend to watch the Flux Index as it is measured directly with reference to radio emissions from the sun.

I begin to get interested when the Flux Index is over 100. Over 100 and the 10 metre band might open to F-layer propagation round the world. If it was to stay over 200 for some days, the six metre band might open for F-layer propagation. At 89 nothing is happening at all.

I have read various things about the relationship between solar activity and Sporadic E. For a 36 hour period 22:10 on 20/7/15 to 11:06 on 22/7/15 I had zero spots on 10m WSPR. This is pretty well unheard of here in July. Right when you would expect to find both Sporadic E and F-layer propagation, there was none of either. For F-layer we do have the "summer doldrums" but the Sun has no seasons, and the flux number applies to all seasons.

Looked at from here, Sporadic E often occurs when the solar activity is high. For example, today there was an opening in Finland, Sweden and Norway on 10m and 6m which was variously called Es or Auroral Es, and the K index is high which indicates incoming mass ejections etc.

The K number and the solar cycle are not directly linked. But I can certainly see high K number causing Es here (at 56 degrees North). The link between the K number and the solar cycle is confusing. Many say that Es is best at solar minima, others say the opposite. Similar conflicting claims are made about auroral activity.

For me, I like to think that whatever the decline in solar activity, my favourite modes of propagation, Es, Aurora and meteor scatter will not be too badly affected. And in this solar cycle we have had only brief spells where the flux index was above 200, and therefore no 6m F-layer propagation at all here. So it looks like I do not have much to lose ... but the Sun will do as it pleases. That huge eruption which will knock out the World's power supplies might be just around the corner.

Despite all this, I am keeping up my new interest in 40 metres. It will be a long time before the solar cycle picks up again. Or at least it will be if the Sun follows the pattern many predict. I am sure that the occasional solar mass ejection will keep me busy on VHF for a long time.

Predicting solar cycles is a pretty sketchy science. Look at this from Wikipedia discussing the different predictions for Solar Cycle 24:-
Prior to 2006, the difference was very drastic with a minority set of researchers predicting "the smallest solar cycle in 100 years."[5] Another group of researchers, including those at NASA, were predicting that it "looks like its going to be one of the most intense cycles since record-keeping began almost 400 years ago."[6]
Well, it certainly was NOT the most intense cycle since records began, and NASA were wrong about that. Perhaps the current predictions are wrong too.

Could I become a 40 metre band enthusiast?

I doubt it.



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