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Solar Cycle 25

Posted: 28 Aug 2017 20:42
by Jim (Bournemouth)
With Cycle 24 now being well advanced on its downward path with solar minimum being expected in many quarters in 2019 or 2020, it is interesting that there are some optimistic signs that solar minimum may be comming sooner than we all think.

IN late December last year, some tiny sunspots at a high latitude with reversed polarity (compared with spots belonging to this cycle) were observed.

(Sunspots belonging to the next cycle generally have the opposite polarity compared with those belonging to the current cycle. Also, new cycle activity appears at high solar latitudes and the spots drift closer to the solar equator as the cycle proceeds.)

Then, earlier this month, another few spots were observed at high latitude also with reversed polarity. This together with some spotless but active regions known as "plage" at high latitudes this month. Then, today, I read this on http://www.solen.info/solar/ -
" The first cycle 25 spot observable at a 1K resolution was noted for several hours today. At noon the active region was located at N43W14, see linked image produced by my automatic spot counting software:

http://www.solen.info/solar/images/2017 ... ots_1k.png

The appearance of a cycle 25 region now could point to a solar cycle minimum in about a year.
This could be very good news.
It may mean that:

**The solar minimum could be sooner than expected.

** It could well be a relatively shallow minimum (the last one in 2008/9 was very deep)

** Cycle 25 could well be larger than Cycle 24 was, though current forecasts based on the extent of solar magnetic fields (which reverse once a cycle, at solar max) currently suggest that C25 will likely be equal or perhaps slightly larger than C24.

We shall see. But it could well be that predictions of a prolonged solar minimum ( "Dalton Minimum" ) could well be exaggerated.

Re: Solar Cycle 25

Posted: 29 Aug 2017 10:51
by John Faulkner, Skegness
Thanks for this interesting article Jim.

Medium Wave DXers won't be happy to read this. But this is quite the opposite of what was predicted for the forthcoming minimum. Being a medium wave DXer myself, I just hope they are wrong and the cycle 25 spots are premature.

Re: Solar Cycle 25

Posted: 29 Aug 2017 12:58
by Jim (Bournemouth)
Cheers John.

The post was written from the POV of an HF DX enthusiast, can understand MW types hoping for a long period of low solar activity!

Re: Solar Cycle 25

Posted: 01 Feb 2018 14:07
by Jim (Bournemouth)
An update. Bit of a rambling one.

If we ignore the peak in solar activity we had at the end of the summer, solar activity continues to drift slowly downward.
Solar flux levels have hovered around the 68-75 range (64-66 is regarded at rock bottom, usually during an average solar minimum, the odd day will see such values), and the running 3 month mean of daily solar flux valuers is 69.. so we are pretty much at solar minimum with regard to activity levels.
Of course, activity could stay low for 2-3 years as happened 10 years ago, but who knows!

We will quite likely see short-term quite small increases in sunspot activity attributable to Cycle 24 regions close to the solar equator over the next few months.

The key thing to look out for is the Cycle 25 sunspot regions.

The occasional region attributable to Cycle 25 have continued to pop up - perhaps half a dozen in the past few months. These are at a high solar latitude (35 degrees plus) and are of opposite polarity to those of the previous cycle.
When these new spot regions start to appear, in the past, official solar minimum has occurred up to about a year later. It is usual to see the old cycle regions continue to appear in tandem with a few new cycle regions, until the latter starts to outnumber the former and mean activity starts to rise. In the last solar minimum, Cycle 24 was so slow to get going that Cycle 23 spots had almost disappeared completely before more than the occasional Cycle 24 spot region started appearing, hence the long and deep minimum last time out. This time, the new cycle spots have shown up rather sooner.

As I previously mentioned, this to me is a strong sign that solar minimum may be sooner and shallower than the 2019/2020 that many are predicting.

The official date of the minimum won't be known until 8-12 months afterwards due to the way the data is smoothed, and centred 6 months either side of the date in question.
For example, if we see a big increase in activity from Cycle 25 regions in, say October, enough to affect 12-month smoothed means, the mimimum may well turn out to be in March this year. Not saying that will happen- it probably won't, but just to illustrate how the timing of solar minimum is determined.

I have a hunch that we *may* start to see Cycle 25 regions in larger numbers later this year.
Whether this will mean solar minimum is officially this year remains to be seen!

Re: Solar Cycle 25

Posted: 01 Feb 2018 18:47
by John Faulkner, Skegness
Thanks Jim.

Very interesting regarding the new cycle 25 sunspots. If we have 2-3 years of solar quiet, that will do me fine. I would hope that the next season sees a BIG improvement in lower frequency propagation. This winter has not shown any signs of a solar minimum in terms of reception, at least not from a MW DXer's perspective.