太陽活動周期
Solar cycle 12 was the twelfth solar cycle since 1755, when extensive recording of solar sunspot activity began. The solar cycle lasted 11.3 years, beginning in December 1878 and ending in March 1890. The maximum smoothed sunspot number (SIDC formula) observed during the solar cycle was 124.4 (December 1883), and the starting minimum was 3.7. During the minimum transit from solar cycle 12 to 13, there were a total of 736 days with no sunspots.