Correct Response: D. The aurora borealis results from electrons in the solar wind interacting with Earth's magnetosphere. The electrons travel along Earth's magnetic field to the poles where they collide with oxygen and nitrogen atoms and molecules in the upper atmosphere. The electrons transfer their energy to the atmosphere, exciting the atoms and molecules to higher energy states. As the atoms and molecules return to lower energy states, they give off light energy. Solar storms do not trigger the nuclear disintegration of radioactive isotopes in the thermosphere (A) and peaks in the solar cycle do not cause stratospheric dust to combust (B). Although solar radiation causes photoionization of molecules in the thermosphere, it is not a cause of the aurora borealis (D).
