The Sun: Variability and Solar Cycles

This lecture discusses the variability of the Sun, focusing on sunspots and the solar cycle. It explains how the appearance and radiation of the Sun change over time, with a period of approximately 11 years. The lecture also covers the correlation between sunspot numbers and radio flux intensity, providing a more accurate way to determine the solar cycle. Furthermore, it explores the impact of solar activity on the density of the atmosphere at different altitudes, emphasizing the effects on satellite lifetimes.