

PayPal - The safer, easier way to pay online.

Is used to describe changes in activity on the visible surface of the Sun during the 11 year long solar cycle. During active times more sunspots are visible on the surface and other phenomena such as solar flares are more readily seen.

A group of sunspots as imaged on July 7, 2012 (credit:- NASA Goddard Space Flight Center / Alan Friedman)
