How to Chase Aurora

As we go into a high point in the solar cycle, I thought it would be fun to chat more in depth about the phenomenon everyone is interested in: Aurora — also known as the Northern Lights. Fun fact: we here in the Northern Hemisphere call it the Aurora Borealis or Northern Lights. But did you know that they also have them in the Southern Hemisphere, and it is called Aurora Australis or the Southern Lights down there?

When my family went to Iceland, we visited the Northern Lights Center to learn all about how it happens and how to predict it better. It all starts with our sun. Little nuclear reactions happen inside the sun when the immense pressure of the sun squishes the hydrogen atoms into helium. This reaction gives off incredible amounts of energy that pushes out towards the surface of the sun. The gas and plasma (charged gas) caused by these nuclear reactions move under the surface of the sun in swirls called convection cells (think cold/hot air currents and how plate tectonics work) and, in-turn, these currents generate the magnetic fields of the sun. Magnetic fields of the sun are constantly shifting due to the reactions.

Then sun spots are formed when strong magnetic fields slow down the convection current and make those spots colder on the surface, thus darker. As the magnetic fields re-align, the plasma escapes from the surface and actually drags the magnetic field further away from the sun. Sometimes, it eventually builds up so much energy it will form an arch from the strong magnetic pull. Once this arch breaks off and leaves the sun, we call it a solar flare. 

The sun is also constantly sending out charged particles into space which we call solar wind. It is the solar wind that actually carries the solar flare energy that makes the aurora on the planets.

For the aurora to actually happen on Earth, a solar flare or a coronal mass ejection has to be facing the direction of Earth. The gas and plasma then takes a ride on the solar winds we were talking about earlier and are taken to Earth. The solar winds can have varying speeds from 300 km/s to 800 km/s (671,000 mph to 1,790,000 mph)! This variation is part of why it is hard to pinpoint exactly when the aurora will hit Earth. It takes roughly 18 hours for the charged particles from solar storms to hit Earth. Solar storms include coronal mass ejections, solar flares, and high intensity solar winds. CMEs are the most common causes of the Aurora large scale Aurora. However, we have been getting a lot of aurora due to large solar flare activity recently.

Once the solar storm hits Earth, it has to pass through the magnetic field (also known as the magnetosphere). The magnetic field around Earth acts as a shield against the cosmic radiation deflecting most of the solar storm and directs it to the Earth’s poles. The poles are the weak spots in the magnetic field and is why a fraction of the solar storm makes it past our fields. After it passes the field, it moves down from the poles and spreads across the ionosphere (next level below the magnetosphere that contains ions and free electrons). For reference, the ionosphere is from 85 km - 600 km above the Earth’s crust. The particles from the solar storm (electrons and protons) excite the oxygen and nitrogen in the upper atmosphere, and the colors we see are determined, primarily, by what altitude in the atmosphere the solar storm particles hit.

The aurora comes in a varying splash of colors: greens, purples, yellows, blues, pinks, and reds. What we see, color-wise, happens from the collision of the excited particles from the solar storm along with the pockets of nitrogen and oxygen in our atmosphere. The altitude these collisions happen at also cause variations in the colors. Green is the most common color that people around the world see. The purples come from ionized nitrogen, green through orange—and a bit of pink—come from excited oxygen, and all the deep tasty reds come from excited nitrogen (as a note, excited elements are where electrons are moved an energy level, ionization is where electrons are removed from the atom entirely). There are many places where you can see the different diagrams of colors but the most important thing is just to get out when the solar action is high and have fun.

There are also different types of aurora: arcs, bands, corona, ribbons, rays, and glow. Now, I haven’t been lucky enough to capture each type of aurora yet, but hopefully, in time, I will. Arcs are when you have the aurora stretch from horizon to horizon, lifting in the middle. Bands change constantly, and their level of distortion will change relative to the level of solar activity. Coronas have a wide range of colors and happen overhead in powerful solar storms—many consider this the ultimate catch for aurora chasers. Ribbons are folded bands and happen when bands overlap each other. Rays are smaller bits of aurora activity and can sometimes be seen as simple pillars of colorful light along the horizon. Glow is just diffused colors all throughout the sky. And then, of course, there is a rare aurora like phenomenon called S.T.E.V.E. (acronym stands for Strong Thermal Emission Velocity Enhancement). It is a little silly, but it is a real thing, and it looks like a straight pillar of light from the horizon going all the way up into the sky. It was only recently discovered and more info on S.T.E.V.E. can be found here.

Now for the “how to actually take the photo” bit! You don’t need anything crazy special to capture it. Some people can even use the long exposure feature on their phones (depending on your phone)—you may just want a tripod to help stabilize your phone for the long exposure. For DSLR and other cameras where you can tell it how you want to shoot using manual mode, suggested exposure settings would be 10 - 20 seconds, f2.8 or as low as your lens/camera will go, and a decently high ISO like 800 or more. These are mere suggestions, and I encourage you to play with the settings depending on the gear you have. For example, if you can only go down to f5.6, you would either go up in ISO or have a longer shutter speed. My suggestion would be, if your camera can handle it, go up in ISO first as the slower your shutter speed with the aurora, the less likely you are to catch defined pillars as the aurora is often in constant motion.

When should you go? The best time is September through April—not saying you can’t see it at other times of the year though—your chances are simply much slimmer with the amount of daylight those times of year have. You’ll want to go out when the moon is new or while it remains a tiny sliver, as the moon gives off quite a bit of natural light pollution. If the solar storm is extremely strong, you can still see the aurora despite the moon; however, that tends to be quite rare. Of course, wear some nice cold weather clothes as it is most likely gonna be chilly out there at night, depending on where you are at. When I captured the Northern lights at Mt Adams on Valentine’s day, it was 20°F, so a cup of hot tea and many layers will help you stay out longer to get some awesome photos. And it should go without saying, that the further out from city lights the better.

Remember, predicting the aurora is like predicting space weather. So sometimes when it hits, it actually hits during daylight hours. Other times it is thought to be a bigger storm than it ends up being or misses Earth entirely. If you thought predicting the rain or snow was hard, this is so much worse.

One of the trusty tools in my back pocket is a phone app called Aurora (I use an android phone, and the app is just called “Aurora”). Another is a website/Facebook page called Solar Ham, which will tell you when the sun is throwing solar flares and what level they are. Last but not least, I would recommend joining a local Facebook group—mine is Aurora Borealis Washington State. I am sure many places have their own, but this is a good way to connect with other aurora chasers and give you insight to where you should go to see it for yourself or if it is anywhere near you.  

So with all that in mind, go out, have fun, recreate responsibly, and go catch some aurora! 

Happy hunting everyone.

Other fun facts about aurora:

1. We recently discovered Mars has an aurora-like occurrence in its southern pole region. However, unlike Earth, Mars does not have a magnetic field that originates from its core any longer. The magnetism that is causing the aurora-like occurrence is actually due to the remnants of the magnetic field found in the crust. More can be read about that recent discovery here.

2. Jupiter also has aurora and we have a mission called Juno which is doing research on it. The aurora is ultraviolet light and actually dims as night falls. There are many mysteries about Jupiter’s aurora and Juno will hopefully find some answers as it will continue its mission through 2025 and more of that can be read here.

3. There are many, many cultures around the world that have myths and folklore regarding the aurora. I found it very interesting in my research that some considered it incredibly lucky to encounter where others found it to be a curse or a monster looking for sacrifice.

4. The Aurora cannot occur in the equator—sorry to all those who live there who yearn to see it. This is because the particles are drawn to the poles and circle out in rings around them. The poles constantly draw energy to them and thus the aurora can’t go that far from the poles without being pulled back. However, historically we have seen aurora as far South as Mexico. The KP index tells us how strong the storm can be and what level latitude you can see it at from kp0 - kp9 with nines being the rarest, only occurring about 4 times in an 11 year solar cycle.

5. On particularly high solar storms you can actually see the aurora through the clouds or even when the moon is out.