A graphical comparison of solar cycles 21, 22 and 23

Cycle 23 peaked at 120.8 in April 2000 and had a second, smaller peak at 115.5 in November 2001. Cycle 22 is not a good comparison due to the unusually short time it took to reach its maximum. Other cycles, particularly cycles 17 and 20, compare better to the development of cycle 23. The X axis in the chart is the number of months since the cycle started, while the Y axis is the monthly smoothed sunspot number.

Chart color overview
Cycle Monthly smoothed sunspot number Actual monthly sunspot number
21 Blue Dark blue
22 Black Green
23 Red Magenta
  • Cycle 21 started in June 1976 and lasted 10 years and 3 months.
  • Cycle 22 started in September 1986 and lasted 9 years and 8 months.
  • Cycle 23 started in May 1996.

Please note that the start dates for each cycle is calculated using the 13-month smoothed monthly mean sunspot number. One advantage of using this statistical (numerical) approach is that the start month of a solar cycle is the same as the month of the solar minimum. It is possible to use other criteria to separate solar minimum and the start of a solar sunspot cycle, however, which criteria to use and how much importance each is given, unfortunately leaves room for individual opinion.
[DX-Listeners' Club] [Solar Terrestrial Activity Report] [Solar Cycles 1-20]