Passage III

Solar cycles are periodic variations in the Sun’s brightness.

Table 1 contains the date of onset for, and duration of, recent solar cycles; the time from a cycle’s onset until the Sun reached solar maximum (the maximum brightness for that cycle); and the number of sunspots at solar maximum.

Figure 1 shows the number of sunspots and the Sun’s brightness at a particular wavelength for part of one cycle.

For the same cycle, Figure 2 shows the number of proton events, when the Sun emitted much higher than average numbers of protons (positively charged particles).