太陽活動周期
Solar cycle 22 was the 22nd solar cycle since 1755, when extensive recording of solar sunspot activity began. The solar cycle lasted 9.9 years, beginning in September 1986 and ending in August 1996. The maximum smoothed sunspot number (SIDC formula) observed during the solar cycle was 212.5 (November 1989), and the starting minimum was 13.5. During the minimum transit from solar cycle 22 to 23, there were a total of 309 days with no sunspots.