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The following Y2K material has been kept available by MITRE for historical purposes only and has not been updated unless noted.
| SUNSPOT CYCLES |
Sunspot records, in the western world, start with the first telescopic observations by Galileo in 1611. Through observations since that time, we've found the number of sunspots follows a roughly 11-year cycle, called the "Sunspot or Solar Cycle". Generally, there is a 4-year rise to a "Solar Maximum", followed by a gradual 7-year decline to a "Solar Minimum". The last Solar Maximum, which was July 1989, had the third largest amplitude on record. The latest Solar Minimum was in Oct 1996.
The next Solar Max is projected to be in the early part of the year 2000. The amplitude of this cycle (# 23) was originally predicted to equal that of Cycle 22, but the actual observed activity levels appear to more closely match those of some of the milder cycles like Cycles 10, 13, 17 and 20. The maximum sunspot count for Cycle 20, for instance, was only 110 versus the 160 count maximum for Cycle 22.
Solar and geophysical activity can and does occur even during Solar Minimum. That is because not all solar activity are solar flare induced--flares are only the primary cause.
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