## 4. Features of the sunspot cycleThe time of the sunspot area maximum, , was given explicitly by the value of for which , then we have is the rising time of a cycle. The value of the sunspot area at maximum, is given by Using Eqs. (3) to (5), we calculate values of
and
of each cycle, which are listed in
Table 1 as well. Here, we define the cycle length The relationship of the rising time and the maximum amplitude is shown in Fig. 5. The thin line in the figure is the regression line of the form
The figure shows that the shorter the rising time of a cycle is, the larger the maximum amplitude of the cycle is. In other words, cycles with large amplitude take less time to rise to maximum, similar to the so-called Waldmeier effect of the sunspot number. A weak correlation between cycle length and the rising time of solar cycles is found and shown in Fig. 6. The linear regression coefficient , and the line is
The figure indicates that cycles that take a long time to get
maximum amplitude tend to run a long time to get ended. The mean value
of the rising time is 5.253 years for the 11 cycles, the average of
the cycle length is 10.883 years. So on an average, the rising time is
less than the falling time of a cycle. We define asymmetry of a cycle
as . Relation between
© European Southern Observatory (ESO) 1999 Online publication: April 28, 1999 |