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regions. These energetic particles excite the oxygen and nitrogen atoms in the atmosphere, producing the
green and red lights of the aurora.
Figure 33.7 shows the aurora as seen by NASA’s IMAGE spacecraft in ultraviolet light. The images are
taken above the Earth, looking down at one of the poles. You can see that the auroræ form anauroral oval
centered on the pole. The figure shows how the auroral oval grows and then dies out with time.
Similar auroral ovals have been observed on Jupiter and Saturn (Fig. 33.8).
Further information on the Earth’s magnetosphere and auroræ is given in Appendix V.