It’s not often we talk about a sizable chance of seeing the Northern Lights in southeast Wisconsin. So many things have to go right for us to see those ghostly shades of red and green dancing across the sky. On Tuesday our chances were about as good as they can get. But it just didn’t work out. The huge coronal mass ejection (CME) hit the Earth’s upper atmosphere beginning early in the day. At night, the light show just couldn’t make it far enough south for our viewing pleasure. And even if it did, it was cloudy.
Years ago I worked for WJFW channel 12 in Rhinelander. I worked the morning show leaving for the station around 3:30am. I remember one morning walking outside before freezing in my tracks. No, it wasn’t the -10° freezing me in my tracks. It was the mesmerizing lights overhead. The Northern lights were out in full force that morning and I was the only one awake, standing on the sidewalk of my apartment complex staring straight up at the sky. I stood there for about 20 minutes before realizing I was going to be late for work.
If you’ve never seen the northern lights on a clear, calm night you have yet to see what I believe is the most jaw dropping scene the earth’s atmosphere provides. Now getting an aurora this far south (Unlike Rhinelander, Milwaukee is closer to the Equator than the North Pole) is a tough task but we’ll have more chances in the next few years.
For the Northern Lights to occur we have to start 93 million miles away at the sun. A solar flare erupts sending a CME speeding into space. The CME is plasma, mainly consisting of charged protons and electrons. These solar flares are much more common during active part of the sun’s 11 year cycle. We are getting near the peak of this cycle which should occur in 2013. Once a CME is detected scientists can quickly determine the speed and direction to make a determination of if and when it will arrive at Earth. While speeds can vary, an average would be 300 miles per second. Thus the 93 million mile trip may take 3.5 days or so. When the traveling plasma hits the earth’s magnetosphere it loops around the earth before dropping in orbit towards the North and South Poles. About 50 miles up the electrons interact with nitrogen and oxygen pushing them to an excited state. Light is released, usually a red or green color but certain interactions at different altitudes can create yellow or blue light which is less common.
The stronger the solar flare the better chance we have of a bright aurora. Tuesday’s CME came from a medium–large flare. Flares are classified by the small C-class, followed by the medium M-class, and the large X-class. Each class is broken up 1-9. Our most recent flare was an M9, just below the X-class. While it’s difficult to forecast when more solar flares will occur and how they will interact with our magnetosphere, we do know more flares are coming during this active part of the sun’s cycle. Let’s hope the next time the CME’s peak arrival is at night and the clouds stay away!
Check out www.spaceweather.com for the latest solar flare and northern lights info.