05-March-2008, 11:19 PM
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Junior Member
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Join Date: Mar 2008
Posts: 43
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I started looking into the Gleissberg Cycle. Most of what I found was vague and arbitrary. Numbers run from 72 to 83. Some references include a 90 year cycle.
I was able to identify what I will call simply a 90 year cycle. I got my data from “Long-Term Variability in the Length of the Solar Cycle.” I have no idea where they got there numbers. I have never seen sunspot minimum date estimates going this far back.
When I started looking at these dates I focused on cycle 16, 1923.8, as my starting point. This cycle is significant because the Spotless Days Cycle (SDC) shifted at this point. If you are not aware of SDC more can be read about the subject here. Also, this is my spreadsheet on spotless days if you interested. I broke down the spotless days by cycle.
I found 3 cycles which were 90, 88.11, and 89.9. Now we are in the 4th 90 year cycle waiting for cycle 24 to start and are currently at 84.7 years.
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