Exploratorium
Exploratorium: Auroras Paintings in the Sky
This site offers a very nice, detailed explanation of auroras along with some inspiring images and videos.
CK-12 Foundation
Ck 12: Physical Science: Plasma
[Free Registration/Login may be required to access all resource tools.] Properties of matter in the plasma state and where plasma is found.
Science Struck
Science Struck: Facts About the Thermosphere
Learn facts about the thermosphere, one of the five layers of the atmosphere.
NASA
Nasa: Heliophysics: New Science of the Sun Solar System Connection
This site from NASA lists common and uncommon misconceptions about Sun-Earth Science. Site also provides links to activities and lesson plans as well as background reading.