Though we refer to the total energy output of the Sun as the "solar constant," changes do occur. Over a solar cycle of about 11 years, particles such as electrons and protons and radiation stream toward Earth with varying intensity and interact with the Earth's magnetic field and atmosphere. The Sun creates sunspots, solar flares, coronal mass ejections, coronal holes, and the solar wind. Some of these phenomena directly affect interplanetary space and the environment around Earth (and other planets). We call these changing and sometimes violent conditions "Space Weather".

Since the early 1800's, all aspects of our technology have been affected by severe solar disturbances beginning with telegraph outages during 1850-1900, radio disruptions between 1910-1960, and then during the Space Age, satellite outages and failures between 1965-2006. Ground-based electrical power systems have blacked out (Quebec, 1989) and airline flight crews have begun to worry about radiation exposure during solar flares. All of these events can be traced to the interaction of the Sun with Earth's magnetic field and its environment in space.

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