'm currently studying the layers of the atmosphere in my science class. I want to mention that the aurora borealis, or Northern Lights, happens when charged particles from the sun enter the atmosphere. The atmosphere isn't perfectly around the earth. It curves in at the north and south poles. The particles enter this "hole" and the gases of the lonosphere (a subdivision of the thermosphere) interact with the the particles, and depending on what gases are in the particles, they appear as different colors to us here on earth. So, really, when we see a beautiful ribbon of light swirling across the sky, there's really a huge battle going on between charged solar particles, and our atmosphere trying to protect us.