Aurora Borealis

Solar features
Flares
Explosive events that normally last an hour or so
Sudden brightening above a sunspot cluster
Release enormous quantities of energy
Eject particles that reach Earth in about one day and interact with the atmosphere to cause the auroras (the Northern and Southern Lights)

Solar interior
Cannot be observed directly
Nuclear fusion occurs here
Source of the Sun’s energy
Occurs in the deep interior

Proton-proton reaction
Nuclear reaction that produces the Sun’s energy
Four hydrogen nuclei are converted into a helium nuclei
Matter is converted to energy
600 million tons of hydrogen is consumed each second
Sun has enough fuel to last another five billion years