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The Northern Lights - a cautionary tale

As solar activity slowly starts to increase more sightings of the elusive Aurora Borealis can be expected. But what can you really see?

Image Credit Grassholme Observatory

The Aurora Borealis or the Northern Lights have to be one of the most awe-inspiring and jaw-dropping sights in our night skies. Hues of greens and reds can be seen to dance across the sky shimmering, glowing and bursting into color with dynamic vibrance. As regular Aurora chasers will testify they can however be very elusive and frustrating to UK observers, but with cameras at the ready snappers have observed them from southern climes in the UK, from light-polluted cities, and mostly it has to be said afterward from their computer screens at home.

The Aurora we see is a direct result of interactions with positively charged particles from the Sun and molecules of oxygen and nitrogen in our atmosphere. These particles are often hurtled away from the sun in violent and turbulent outbursts known as Coronal Mass Ejections, or CMEs. If our home planet is in the firing line then it's game on, as a few days later, once those particles arrive those interactions can begin, which are collectively referred to as the Solar wind. Those CMEs can be expected to become more frequent due to the Suns cycle ebbing and flowing over an 11-year period. In 2025 we can expect the Sun to be at its most active on that cycle, we call it Solar Max. So get ready for more alerts more Apps to download and ultimately more disappointment.

A bit about the science first.

Our planet is protected from harmful radiation from space by our large and complex magnetic field, the main source of this radiation is the Sun. Some radiation however can penetrate our magnetic field, light for example can but that is not the end of the resistance.

Our Atmosphere has with the Sun nurtured life here on Earth for billions of years, it protects us, stores the air we breathe, and gives us beautiful blue skies (sometimes). It's that air we breathe that upon excitation produces light. In physics, we see this process repeated many times, and a whole bunch of fundamental physics (if not all!) is based on the interactions of particles, magnetism, and light. In cosmology, we can see new star formation in clouds of molecules nestled in the spiral arms of galaxies, through pretty much the same fundamental physics that produces the Northern Lights.

Atoms, you see like nothing better than to be at rest, It turns out that a natural state of the universe is to be in its lowest state of energy. That same effect is repeated with us too. As you read this I'm pretty sure you are sat down rather than doing a 10K run! So why does this matter? well, when said positively charged particle rams into gas in our atmosphere it excites electrons in the atom, by discharging a tiny amount of energy to it upon collision. The electron however will return back to its 'ground state' (lowest state of energy) by spitting out some energy. When this happens that energy can be measured and will have a wavelength, if it corresponds to the visible light we can see, we will see it. If the wavelength is long it may appear red, shorter, and it will appear greener. This, in a nutshell, is what happens in nature that allows us to see the coloured lights we all crave.

So how do they differ so much depending on location?

Well, this has everything to do with the distribution of the magnetic field and its orientation. Most adults know that the magnetic field that propagates from the earth's core is a dipole field, meaning it has a positive polarity and a negative polarity (They all do BTW) it also has a shape like a big apple in section. We can see it when we encounter total solar eclipses, here the entire disk of the sun is eclipsed by the entire disk of the moon. This allows observers to see the Suns magnetic canopy.

The Suns magneic foeld during eclipse

So that magnetic field propagates through the entire solar system and gets the catchy monicker of the Interplanetary Magnetic Field or the IMF. The fact that the magnetic field emanates from the earth's core means it literally has holes at the poles and it's these holes that allow trapped particles to cascade into our atmosphere and produce the light show through interactions.

We humans like nothing better than a good interaction, especially if it involves light and colour. So it's no wonder that we flock to the furthest frigid parts of the planet to try to get a teasing glimpse of the elusive lights in the sky and now is a great time to do it. But tread carefully, as there are traps set and waiting for you to falter.

The first thing I would always mention is to be aware of the Moon, its big bright and has phases, if you do decide to go to the frozen arctic, choose a period when the moon isn't going to be around and you get the skies at their darkest.

The second point is for me the big one, especially for UK observers.

Firstly, picture the scene, a casual glimpse at Facebook, Twitter or Insta and you see auroral images from next door - greens and reds, they are bright and they happened last night and you missed them! how could this happen? I mean if the sky looked like that you must have seen them I mean everyone must have seen them - right? well no, why? because they didn't look like that - confused? you should be!

After image processing

Please explain - Ok, firstly our eyes take a lot of photons in and send them off to our brain, our brain then takes around 30 exposures a second and builds an image, so we see the world as a gap-filled video. That image you saw on SM over your cornflakes, like the one above was taken with a camera and then pushed through Photoshop then rammed into an SM channel and then has 450K likes and is not what the sky looked like at all - its a rendering a glimpse through the eye of a DSLR camera that probably cost at least £1000 - but it got the likes, which is the point. On a good night the below image is more of what you could have expected to see.

What you can expect to see

So the images you see on SM arent anything like what was actually visible to the observer taking the image. Imagine turning down the volume on the colour squinting your eyes so you can just about see faint light and you are somewhere near to seeing what was visible.

Sometimes however nature can turn up the volume for us, if the solar wind is fast and dense then that can be enough to charge the atmospere up like a battery and then it discharges into the atmosphere and we can occasionally see it a little brighter.

But to truly see it in all of its super charged glory now is the time, just head North to one of the locations beneath where our magnetic field leaves the earths surface, under what is referred to as the aurorla oval, and wait, and wait and maybe you will see them free from photoshop and hungry SM types thriving on likes and distorting reality.

I have been fortunate enough to see the northern lights many times from my place of work but rarely have I ever seen anything that looks remotely like what I see on my computer screen or on a socail media feed, unless I found myslef in Norway, and that was a different story altogether.

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