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Thursday, June 04, 2009
Sunspot Minimum at Hand

By Joseph D’Aleo

The sun has become more active in recent days with cycles 24 spots in middle latitudes. See sunspot group number 11019 for group of red spots. This is slightly diminished since yesterday. The dark green areas are coronal holes out of which the solar wind escapes at higher velocity.

See larger image here.

Peter Lawrence has a close up view of that sunspot posted on

See larger image here.

There is a loop of the sunspots develop and rotate around the solar disk the last few days here.

This activity came late enough in the month of May, to keep the monthly number for May below the value of 14 months ago of 3.2 which it is replacing in the 13 month running mean. That means the solar cycle minimum canít be earlier than November 2008, making it at least a 12.5 year long cycle 23.

The value needs to fall below 3.4 in June to move the minimum to December. That is still possible if the sunspot group continues to decay as most have done as they crossed the disk in recent months. If it stays below that value, we will likely see the solar minimum in December, 2008 as 14 months before that the sun was very quiet with just a sunspot number of 0.5. If not, the minimum will be November. It is my guess that November will win the prize. 

We added 22 more sunspotless days to the total for this cycle transition which as of June 1 had now reached an amazing 614 days. We are likely to add additional days and add 2009 to 2007 and 2008 as recent years in the top ten since 1900. Only the early 1900s had a similar 3 year stretch of high sunspot days (1911, 1912, and 1913).

See larger image here.

It also marks the longest cycle in 150 years, tying the one that peaked in 1848. You have to go back to the Dalton minimum in 1816 to find a longer cycle 12.7 years.

See larger image here.

You can see in 3 of the 5 most recent cycles, the sun had rebounded significantly by years 12 and 13 into the next cycle.

See what some scientists believe this means about the decades ahead here.

See also this story in DailyTech from NASA and this Icecap Library post on solar.

Posted on 06/04 at 02:09 AM
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