Final answer:
Auroras occur in the ionosphere, a part of the atmosphere. Charged particles from the solar wind interact with the Earth's magnetosphere and cause molecules in the ionosphere to glow, creating the auroras.
Step-by-step explanation:
Auroras occur in the part of the atmosphere called the ionosphere. When charged particles from the solar wind reach the Earth's magnetosphere, they follow the magnetic field lines towards the North and South poles. As these particles collide with molecules of air in the ionosphere, they cause them to glow, producing the beautiful curtains of light known as auroras.