Every 11 years, the sun completes a solar cycle of calm and stormy activity and begins a new one.
원문출처 : https://www.cnn.com/2020/09/15/world/solar-cycle-25-nasa-noaa-scn-trnd/index.html
원문출처 : https://www.cnn.com/2020/09/15/world/solar-cycle-25-nasa-noaa-scn-trnd/index.html