PHOENIX — So far this year, Arizona has been treated to the best sky shows we've ever seen. In May and October 2024, the Aurora Borealis, or Northern Lights, were visible here in State 48.
What are the Northern Lights? The Aurora Borealis is the result of electrons colliding with Earth's upper atmosphere. When energetic particles are snapped back toward Earth's atmosphere, they tend to travel along Earth's magnetic field lines.
Typically, this is in the polar regions. But when Earth's magnetic field becomes super disrupted, like a geomagnetic storm or solar activity, sometimes this can get displaced toward the lower latitudes. Since Arizona is at a lower latitude, we see red auroras.
"What a lot of people in Arizona have been seeing is red aurora. Ones that are very high in the sky. You can see those on the horizon," said ASU Assistant Professor Katrina Bossert. "They're not overhead, but you're looking on the horizon at them. That's where you get these pictures of displays where you can see the red and sometimes you can see them down into the green."
The different colors indicate how high in the sky the electrons collide with molecules in our atmosphere. Red Auroras, like the ones we've seen recently in Arizona, occur above 200 kilometers. Green auroras are 100 to 200 kilometers, or about 124 miles up in the sky.
So why has Arizona seen the Northern Lights more now than ever before?
"We're seeing a lot of activity right now because we are in solar maximum...So the sun's magnetic field flips polarity every 11 years or so, and when it's in the middle of that things get very unstable on the surface of the sun, so we get a lot of solar flares, a lot of mass ejected from the sun, and that's called a coronal mass ejection," Bossert explained. "This can influence the earth pretty significantly. The storm that happened back in May was the most severe rating of a storm. We tend to say that those only happen once a solar cycle."
The big-time aurora shows happen roughly every 11 years. Even though we have an idea of when auroras will be visible, it's not an exact science.
"Last solar cycle we didn't have any. It was a quieter solar cycle, so now we're in this state where we haven't seen a solar cycle like this, we haven't seen a solar max like this for 20 years," Bossert said.
And 20 years later, we have technology that allows us to share our view of the sky's most breathtaking light display. If you've missed out, there's still plenty of time for the next big show!
"We are in solar max right now. These solar coronal mass ejections, these solar flares, and solar active regions are more common....and they are going to be more common over the next few months and possibly over the next year," according to Bossert.
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