sunspot number

Sunspot number is a measure of the activity on the Sun's surface, counting the number of sunspots and groups of sunspots visible at a given time. It helps scientists track the Sun's solar cycle, which varies over about 11 years. More sunspots indicate higher solar activity, which can influence space weather, satellite operations, and Earth's climate. The sunspot number is calculated using a standardized formula that accounts for individual spots and groups, providing a consistent way to monitor changes in solar behavior over time.