
doi: 10.1007/bf02001092
Within each sunspot cycle the yearly means (A) of the daily sunspot areas increase faster than the corresponding sunspot numbers (R) from the minimum to the maximum of solar activity and then decrease also faster than these numbers till the next minimum. Relation (A)=16.7 (R), frequently used so far, is approximately valid only for the years in the vicinity of the sunspot maximum. Instead of that, author gives the relations: $$(A) = \left[ {a + b\cos ^2 k\frac{\pi }{{2{\rm T}_R }}} \right] \cdot (R)$$ for the years preceding the sunspot maximum, $$(A) = \left[ {a + b\cos ^2 k\frac{\pi }{{2(11 - {\rm T}_R )}}} \right] \cdot (R)$$ for the years following the sunspot maximum, wherea andb are constants,T R is the time of rise of the corresponding sunspot cycle expressed in years, andk takes the valuek=0 for the year of maximum solar activity andk=1, 2, 3, ... for the first, second, third ... year preceding or following that of maximum solar activity. The monthly means of the daily sunspot areas show a similar variation, but in this case the ratioq=A∶R varies with a greater amplitude both within each sunspot cycle and from cycle to cycle. The values ofq corresponding to all months of a given year in the sunspot cycle are contained between two limits depending on the time of rise.
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