In Awe of Auroras
How come people outside the Artic Circle could view them over this weekend?
As I am deep in studying for exams season, I wanted to keep this one shorter, but something peculiar that happened this week.
This weekend was a special event in the northern hemisphere, the Borealis Aurora, more common known as the Northern Lights. Now these lights are typically only visible in the Artic Circle so how come that people in Portugal were able to see it and how do they work?
What are the Northern Lights?
Every second of the day highly energetic particles get ejected from the sun and fly towards the Earth. When nearing it they start to be influenced by a shield, set up by Earth’s magnetic field that deflect these around it, resulting them to be deflected to the north and south poles. By the time it has reached these poles, they are a lot closer to Earth, more specifically these solar particles lie within the ionosphere. The ionosphere consists of multiple sub-layers including thermosphere and parts of the mesosphere and exosphere and is anywhere between 48 to 965 km above the surface1. The reason its called the ionosphere is because this is where ions lie. An ion is an atom or a molecule that either has a positive or negative charge and its these ions that interact with the sun’s energetic particles.
When they interact these ions absorb the energy and the electrons within the atoms get excited. When they relax, they release this energy in forms of photons, or light in a certain colour. Each element when burnt (or excited) has a unique colour to it, its like a fingerprint which scientists use to analyse which elements materials are made of. This is a whole field on its own called colour spectroscopy and varies with applications in forensic science to analysing the chemical composition of Exo Planets and their atmospheres. With this in mind, what elements are the colours of the aurora?
Understandably, they are the elements that make up out atmosphere, the fluorescent green/ yellow is caused by oxygen, where the blue and red colours come from nitrogen. Occasionally you will have small traces of other colours like orange (cause by neon) too2.
Why could we see it much more south?
The fact that the intensity of these auroras have increased isn’t unusual, but the fact that people in Portugal were able to see them has only happened twice in recorded history, the last occurrence was 90 years ago. This sighting was caused by a huge geomagnetic storm instigated by a huge solar flare ups. Every 11 years the sun undergoes a cycle in which it experiences a solar minimum and maximum, the difference in activity can be seen in the image below.
During these solar maximum’s, you can have particularly intense storms which range up to G5 being extreme, which was experienced over the weekend. Here the solar radiation that hits the Earth’s outer atmosphere can be so intense that it can disrupt radio transmission and navigational tools like GPS3. This level of storm is rare but not a once in a lifetime event with the last G5 storm being in 2003, meaning it can happen again!
If you are looking to catch the auroras, don’t wait! Go to the Artic Circle in the middle of nowhere to experience them first hand, and make sure you bring your camera, as they capture it better than your eyes can see. Here is a photo that was captured from my garden in Bristol on Friday night, bare in mind with the naked eye, barely anything was visible.
Till next week,
Maxime
Ionosphere - Space.com
https://www.space.com/ionosphere.html
Why are the Aurora Lights Different Colours - Aurora Nights
https://aurora-nights.co.uk/northern-lights-information/what-are-the-northern-lights/why-are-there-different-colours/#:~:text=Oxygen%20gives%20off%20the%20fluorescent,while%20neon%20turns%20them%20orange.
Severe Geomagnetic Storm Issued - CBS News
https://www.cbsnews.com/news/severe-geomagnetic-storm-watch-issued-unusual-solar-event/#:~:text=G5%20is%20the%20strongest%20level,experience%20complete%20collapse%20or%20blackouts.
Wow, that was fast and on the ball. Now we can immediately understand what many of us saw in Western Europe this weekend. Interesting, also for the uneducated ones on the topic.