What do the lines in this NASA graphic represent?

Why does Solar cycle 22 have a peak of nearly 300 (assuming that peak represents the maximum observations at the same time) and this link says the peak is 212)?

enter image description here

  • $\begingroup$ No, its not. The official number of maximum sunspots observed in Cycle 22 are 212 (see the link above) and the graph show something up to almost 300. That is my question. What is almost 300? $\endgroup$
    – Max
    Feb 26, 2018 at 12:34
  • 1
    $\begingroup$ The white, smoothed curve looks like the smoothed variant of the white spiky curve. White and spiky goes near 300, white and smooth goes near 212 (more like 220). The error envelope of the smoothing is the white dashed. $\endgroup$ Feb 26, 2018 at 14:13

1 Answer 1


In the above plot by Hathaway, the jagged line peaking at 284.5 in June 1989 is the monthly international sunspot number. The smooth curve starting and ending a few years later is a prediction based on recent observations and statistics of past cycles.

The peak of 212.5 in November 1989 is for a 13-month smoothing of the monthly number. The Sunspot Index and Long-term Solar Observations (SILSO) project at the Royal Observatory of Belgium archives these data and provides this plot of the monthly and smoothed sunspot numbers together. SILSO plot of monthly and 13-month smoothed sunspot numbers


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