Hi Bronagh! I ve seen some, they are incredible to watch! How is this beautiful sight produced? Well, our sun is continually spewing positive positively charged ions into space. The flow of these ions is called the Solar Wind and when the particles that make up this wind near the Earth, they tend to be funneled toward the poles of the Earth (due to it’s magnetic field). As they reach our atmosphere, they are moving very fast and knock electrons (the negatively charged bits of atoms) out of atoms in the upper atmosphere. When those loose electrons are caught by another atom, light is emitted. The color of light depends on the type of gas, or atoms, involved. For example, green is oxygen, red hydrogen, and blue nitrogen. The resulting light is what we see as the Northern Lights, or Aurora Borealis. Hope that helps!
… and sometimes when there is quite a lot of solar activity this energy can overpower our earths magnetic filed and come further south from the poles. There were northern lights in Ireland about 10 years ago! I remember watching them over Dublin!