Northern lights may light up Michigan's skies this week

Hani Barghouthi
The Detroit News

The northern lights may illuminate parts of Michigan on two nights this week. 

Geomagnetic storms are expected from Wednesday night until Friday morning, according to the Shawn Dahl, a forecaster with the National Oceanic and Atmospheric Administration's Space Weather Prediction Center. 

A minor storm watch is in effect early Wednesday evening and a moderate watch is in effect for Thursday night, Dahl said, adding that the forecast has changed "a lot" since it was first announced early Tuesday and would likely continue to be adjusted. 

The most significant event, a strong geomagnetic storm expected to take place late Wednesday evening into early Thursday morning, will be the result of charged particles hurtling toward Earth's upper atmosphere at an estimated 522 miles per second, according to the prediction center. 

The northern lights, or aurora borealis, form when those particles — electrons, not protons — collide with the upper reaches of Earth's atmosphere, creating dancing waves of colorful light in the sky. 

The eruption of particles is the result of an event called a Coronal Mass Ejection, referring to the corona, or the outermost part of the sun's atmosphere, which produces solar wind. Two ejections occurred this week, according to the prediction center. 

Starting at 8 p.m. Wednesday through 5 a.m. Thursday, the lights, which dubs the "Holy Grail" of skywatching, may be visible in portions of northern Michigan and the Upper Peninsula, depending on the strength of the geomagnetic storm. 

That is assuming clear skies and low light pollution, of course. 

How to know where northern lights will be visible

Storm strength is indicated by an activity index that uses data from magnetic observatories around the world to measure disturbances to the planet's magnetic fields. The index uses numbers from 0 to 9: the higher the number, the stronger the geomagnetic storm.  

Combined with location data, the Kp-index can help determine how strong a storm needs to be for residents to be able to see it.

The Kp-index value in Michigan ranges from 5 in the Upper Peninsula to 7 just north of Detroit, according to See the Aurora, meaning a storm would need to be classified as "minor" to be visible in the U.P., but "strong" near Detroit. 

On Wednesday night and early Thursday morning, the Kp-index for the coming storm will reach its peak, Kp6, from 11 p.m. to 2 a.m., according to the prediction center's three-day forecast as of early Tuesday afternoon. 

Here's where the northern lights could be visible:

  • At Kp6, people in the U.P. as well as those north of Houghton Lake in Lower Michigan might be able to see the sky light up.
  • From 2-5 a.m. Thursday, Kp-index will be 5, meaning the lights may be visible in the U.P. only. 

What else to know about northern lights

Northern lights work in a way similar to neon lights, according to NOAA. 

In the collisions between the particles from the sun and Earth's atmosphere, the electrons transfer their energy to the atmosphere, exciting the atoms and molecules to higher energy states. When they relax to lower energy states, they release energy in the form of light.

The Northern Lights most frequently appear in a radiant green color, but blue, yellow, pink and red are also possible, according to the Aurora Zone. The color of the lights is dictated by the gases with which the electrons collide, which vary based on altitude.

Green is the most common, because most solar particles typically collide with our atmosphere at an altitude of around 60 to 150 miles, where there are high concentrations of oxygen.

The Northern Lights are not the only product of this process. When it occurs in the Southern Hemisphere, aurora australis, or the Southern Lights, are born.