If you missed the display of Northern Lights over the past weekend, keep two things in mind: It was great but not as great as pictures make it seem, and there’s a pretty good chance you can see it again over the next few months.

The Northern Lights, as well as the Southern Lights on the other end of the planet, are caused when the sun throws off charged particles that interact with various portions of the atmosphere. The sun goes through a roughly 11-year cycle in which its magnetic field shifts position due to the movement of the electrically charged gases that make up the ball of flame.

In the middle of this 11-year cycle, we hit the “solar maximum” when the most particles are thrown off, meaning auroras are most frequent and strongest. The current cycle started in 2019 so we’re in this maximum now and will be through the fall, which explains why there’s a good possibility of seeing more atmospheric luminosity over the next few months.

NOAA has a website that predicts where the Northern Lights (and Southern Lights in case you’re going to New Zealand) will be seen over the following 30 minutes. 

Incidentally, the solar cycle is beloved of climate change deniers who want to blame it for our bad weather, but those who understand the topic say this is wishful thinking. Solar bursts can endanger satellites – the weekend display disrupted some John Deere navigational systems used in tractors, leaving farmers unable to plant crops –but they aren’t heating up the ocean, multiplying tornadoes or spreading drought and floods. 

The colors seen in auroras depend on which elements are being heated by the incoming solar particles. Nitrogen turns blue or pink and oxygen turns green, although astronomers say a really energetic aurora will excite oxygen that is very high up in the atmosphere, producing a bright scarlet.

Before we go further, a quick reminder from high school biology about our eyes. As you may recall, our retinas have two kinds of light-sensing cells: rods and cones.

Rods are very sensitive to light but don’t see color. They are located around the edge of the retina, which is why you can see things better in very dim light by looking slightly to one side of them. Cones can see color and are in the middle of the retina, but they’re relatively weak.

As a result, it is quite possible for our rods to detect the light patterns of an aurora, the spikes and pillars and the pulsing bands that sweep across the entire sky, without our cones detecting any of the colors. In that case, the aurora will look pale white, like high clouds illuminated by a full moon.

Cameras are much more sensitive than our eyes so they pick up far more of the aurora colors than we can see. This is particularly true for modern digital cameras. So the pictures show what the eye might have seen.

As more than one person commented this weekend, the aurora was the exact opposite of the solar eclipse. The eclipse looked astonishing in person but most photos of it were disappointing, while the aurora was fine to look at, but the photos were much better. 

Either way, they’re both worth seeing and photographing.