Every once in a while, an intense burst of radiation will expel outward from the sun’s atmosphere toward space. The flare will contain the energy of a billion hydrogen bombs and send billions of subatomic particles called protons and electrons hurtling toward the Earth.
The massive solar ejection may pummel into Mercury, damaging its exosphere and stripping material away from its surface. The flare then could hit Venus, causing ions to be flung out of the planet’s gravitational grasp and weakening the atmosphere.
Next, if Earth’s orbit is in the right place at the right time, the solar flare will crash into the planet…causing pretty lights in the sky.
These are called the northern lights, or the aurora borealis, and occur around Earth’s north pole. A similar phenomenon called the southern lights, or aurora australis, also occurs around the south pole.
And sometimes, you can see the northern lights in Idaho.
What exactly are the northern lights?
When pretty colored lights randomly appear in the sky, there’s usually some weird science going on.
But in its simplest form, the northern lights occur because the magnetically-charged protons and electrons encounter Earth’s magnetic field, which protects the planet from cosmic radiation and particles emitted from the sun. The protons and electrons follow the magnetic field, which convenes at the north and south poles.
That’s when the magic happens.
“When (protons and electrons) slam into the atmosphere, they excite the atoms there, and oxygen happens to glow green,” Jason Barnes, a professor in the University of Idaho Department of Physics, told the Idaho Statesman in a phone interview. “And so a lot of what you’re seeing is oxygen glowing in the upper atmosphere.”
Barnes hasn’t worked directly with Earth’s aurora borealis, but he’s worked in-depth with the Cassini Spacecraft on spectating a similar phenomenon on Saturn.
Barnes also explained that oxygen isn’t the only molecule with atoms getting excited by the solar flares, but that it’s the most dominant molecule in the atmosphere and the one we can see easiest with our eyes.
How often do the northern lights occur?
The Northern Lights are always present near the poles because protons and electrons from the sun are consistently hitting Earth.
But the large solar flares can cause the lights to sometimes show up as far south as the continental United States.
“When the solar wind is stronger and blasting more material out into space, it will sort of start to overwhelm Earth’s magnetic field,” Barnes said. “And that will cause the latitude of the aurora to go down to lower and lower latitudes.”
Astronomers and physicists predict how far south the northern lights may venture by measuring the strength of the solar winds on a measurement called the K-index. The K-index typically stays below a value of 4, Barnes said, which would mean the northern lights don’t venture too far south.
But when the K-index starts to measure above six, there’s a chance for those in Idaho to see the sky lighting up above them.
The sun goes through an 11-year sunspot cycle, swinging between the sun having lots of sunspots on its surface and then nearly none at all — sunspots are what cause larger solar flares.
“Right now, we’re on the upswing in the middle of the solar maximum, so there’s a lot of solar activity these days,” Barnes said. “And so there’s a much better chance of having one of these high K-index indices that would allow Aurora to get this far south these days than three or four years ago. And similarly for five or six years from now.”
How to view the northern lights in Idaho
In Barnes’ words, the aurora doesn’t care what time of the year it is: “It’s just going to do its thing.”
But there are ideal conditions to watch them. It gets darker much earlier in the winter, meaning viewers don’t have to stay out as late to try to catch them. But there’s also typically a higher chance of clouds during the winter, meaning summer viewing is best for clear skies.
Barnes also recommends somewhere away from light pollution, but says he has seen the lights in Idaho around the town of Moscow. He also said the Central Idaho Dark Sky Reserve would be a good location — the reserve is just 10 minutes northeast of Pettit Lake’s eastern shore and boasts one of the darkest skies in the United States.
Once you’re in a dark location, the next challenge is identifying the lights.
“It kind of looks like a thin cloud. But it kind of changes really fast. So it changes on maybe 20 or 30-second timescales,” Barnes said. “And that’s really the big indication that you’re looking at an aurora and not just a random cloud.”
Auroras can be viewed with the naked eye. Barnes recommended against using any sort of telescope or binoculars because an aurora is a wide-scale event, and a magnification device may limit your view.
