Aurora Borealis - The Northern Lights

Unfortunately the northern lights were a no show last night.  There just was not enough energy to produce them this far south in the states (at least southwestern Wisconsin that is).  However, like I promised, I will explain what causes these atmospheric light shows!

It all starts 93 millions of miles away on that glowing fireball we call the sun!  Our sun is constantly emitting charged particles, byproducts of its thermonuclear reactions.  Together, these particles form what is known as a solar wind which travels away from the sun at speeds up to a million miles per hour!  At its top-end speed, a solar wind could reach Earth in as little as two or three days!  Normally, the Earth's magnetosphere (or it's magnetic field) deflects the normal solar wind that comes our way every day.  However, when there is a solar flare or a coronal mass ejection from the sun, much similar to Sunday's event, the solar wind is much, much greater!  This increase in energy disturbs the normal balance between the solar wind and the Earth's magnetosphere.  As a result, electrons and protons within Earth's magnetic field are accelerated and travel down magnetic field lines to Earth's poles.  Here, these charged particles collide with atoms and molecules of the upper atmosphere (typically O, N, and N2) and actually pass their charge onto the atoms and molecules, forming excited states of these gases.  As these gases release the energy and return to their normal state, they give up the energy in the form of light - producing the aurora!

You may have noticed that auroras have various colors as well.  The specific colors we see in an aurora all depend on which atmospheric gas is stuck by the energetic particles.  Oxygen is primarily responsible for two different colors, a green-yellow light and also a more rare deep red light.  Nitrogen, on the other hand, can produce either a blue light or a purple-reddish light, typically seen at the border or edges of an aurora.

I hope this answers some questions... and it may have you coming up with more!  Just ask, and I will try to answer any questions about auroras that you field my way!