Auroral Phenomena

The aurora is the visible excitation of the gases above the ionosphere by energetic electrons and protons. The auroral patterns are strongly influenced by the geomagnetic field, forming curtains and rays along the magnetic lines of force. The details of the optical excitation in the aurora are very complicated and not well understood. It is clear that both electrons and protons are necessary and that these exciting particles must be accelerated in the vicinity of Earth. We have only rough and untested ideas as to how the protons are accelerated, and why the auroras show a preference for latitude ±65°. We do not understand how and where the electrons are accelerated, or why auroras should have a curtain and ray-like structure, or why the aurora is a night side phenomenon. We wonder to what extent the aurora is associated with the radiation belt around Earth.