Question: How do norphen lights form? Why only in cold countries?

Lisa Baddeley answered on 5 Mar 2018:

Hi,
The northern lights form when small particles from the Sun (mainly electrons and protons) collide with nitrogen and oxygen atoms and molecules in the Earth’s atmosphere. When they collide the nitrogen and oxygen get more energy and they don’t want to have this energy. To get rid of it they emit a photon of light. The colour of the light will depend on whether it’s oxygen or nitrogen – you have green and red aurora with oxygen and blue aurora with nitrogen.
The aurora only occurs close to the magnetic north and south poles and is also due to the shape of the Earth’s magnetic field. It just happens that the magnetic poles are also near the geographic poles where it’s very cold. In the northern hemisphere you have the aurora borealis and in the southern hemisphere you have the aurora australis.
I hope that answers your questions 🙂