Tonight due to powerful X-class solar flares earlier this week we may get to see the Aurora Borealis at latitudes where it usually is not visible.    The Northern Lights are the result of charged particles from the Sun interacting with Earth's magnetic field.  They ride the lines of magnetic force towards the north and south pole and release light as their acceleration changes.   



This is one of the most beautiful sights in nature. A view of the Aurora Australis from the international space station.

Why can't we see these in the 48 Contiguous United States of America, or very far south of the Arctic circle more of the time? 

The reason we don't see this phenomena more of the time is simply that the number of particles interacting with the magnetic field at lower latitudes is too low. The density of these interactions in the sky is too low. The same phenomena of particles interacting with Earths magnetic field occurs father south, but the low number of such particles and the low density of them, where the field lines are more spread out, far from the poles, means a very low intensity that cannot be seen. I can say this is so, because if it wasn't cosmic rays and solar wind particles would cook our DNA. At the poles particles are concentrated by the magnetic field causing an incredible light show.

When an intense solar flare as occurred earlier in the week hits the earth the intensity of the interaction turns up to where it may just be detectable farther from the Arctic circle.  

There is an outside chance, I'd put it at 1%, that it could be visible as far south as 38 degrees North.  However the chance of seeing something increases greatly the father North you are, and the darker the viewing location.   For what it's worth spaceweather.com is reporting sightings as far South as Arizona already.  I'm skeptical of that but it's not impossible. (their website is down now, here's the cahced Google version.) 

You should go and take a look anyway. 
The Aurora is just significant enough of a sight that, if it's not cloudy, then going out at midnight just to take a look would be worth it.  Even if it's not a strong Aurora, seeing it from your suburban porch would be better than needing a team of sled dogs, or a Canadian/Alaska Bush plane to get far enough north to see it for sure.   The loss of missing this sight would be greater than the loss of looking and not seeing it.   
Citations


Denver Post

USA Today


Update

Sadly it was too overcast over and around Chicago for me to see much of anything.  Here are links to some good images of it as it would've looked this far south.

From Bangor Maine 

Last night was the best viewing opportunity, but it may also be visible this Saturday night.The odds of viewing are lower tonight...but if you see an eerie glow on the usually dark norther horizon, you will be seeing the northern lights.