Hank Green of SciShow explains in very understandable language how auroras are formed in answer to a fan’s question about the subject.
Make no mistake. People say solar wind which makes it sound pleasant and breezy, but it’s plasma – high-energy high-speed super hot particles that are byproducts of the fusion happening inside the Sun. That wind packs quite a punch and actually distorts the shape of our magnetic donut squashing it on the side facing the Sun and in blowing it out into a long tail on the other side…So those super hot, super fast particles get deflected by our magnetic field and instead of smacking us in the teeth, they flow along the field lines toward the north and south poles and they hit our atmosphere around the holes of the donut to wherever those holes are. That’s where you see auroras, because that’s where the charged particles are actually hitting the Earth.