Figure 5-21 RIVUXG The Aurora (a) Captured by the NASA IMAGE satellite, this glowing aurora oval is about 3000 mi (4500 km) in diameter and centered over Antarctica just four days just after a record-setting explosion on the Sun. (b) This view from Alaska shows aurorae at their typical altitudes around 100 mi (160 km) above the surface. The green color is from excited oxygen atoms and the red from nitrogen molecules in the upper atmosphere.