Did you see the aurora at the weekend? Are you desperate to see it again? Or even just wondering what the “northern lights” actually are?
Guest Blog by Ishbel Carlyle. Photography by Mike Bolam.
Photos: Aurora Borealis at Crawick Multiverse by Mike Bolam (10 May 2024) See full album here.
THE SUN’S ROLE
The Aurora may seem so ethereal because it is not actually caused by anything here on Earth. It is all to do with the Sun.
The Sun is made up of plasma, the extreme high-energy 4th state of matter. As with most extremes in physics this means it has some weird properties. For example, the Sun is spotty. It has loops of the plasma coming out of the surface whose feet we can see as dark spots on the Sun. When we look at different types of light such as ultra violet we can see these loops, they make the Sun look hairy. These loops are actually magnetic fields.
Figure 1: Image Credit Solar dynamic Orbiter NASA, UV image Photo credit: Mike Bolam – Solar Disk with Sunspot AR3664, 10th May 2024
Maybe think of the loops not as hairs, but as elastic bands. What happens when you stretch one of those too much? SNAP! Same thing happens with the Sun loops and all the Plasma that was suspended in the loop is thrown out into space. Basically, the Sun burps. And sometimes Earth gets a face full.
SOLAR ACTIVITY AND THE 11 YEAR CYCLE
The amount of burps changes on an 11 year cycle. Every 11 years the sun gets spottier, then less spotty. Why? We do not know. Yet. Currently we are heading for the peak of the activity going into 2025. So, the next few years are going to be great Aurora-Hunting years. The more spots, the more loops and the more plasma potentially being thrown our way.
But we do not see something like last weekend every 11 years, so what happened? Well, the Sun did not just burp, it puked. There is such an active spot section (Region 3664) on the Sun that it spewed out some of the biggest ejections of plasma in recorded history.
HOW THE AURORA GLOWS
So what happens when the plasma from the Sun reaches us? Is it the plasma we see in the atmosphere? Not exactly. The plasma is charged, so when it interacts with our very own magnetic field it is channelled to the north and south poles where the magnetic fields are the strongest. Our magnetic field is shaped a bit like a bar magnet. When the charged particles are accelerated along our magnetic field into our atmosphere, they collide with the atoms in our atmosphere which in turn glow. This is what we see as the Northern and Southern lights. The more particles pummelling into our atmosphere in the north and south, the further down towards the equator the effects can be seen.
Figure 2: Image credit GoOpti (https://www.goopti.com/en/about/goopti_blog/aurora-borealis-where-to-see-the-northern-lights-in-2020)
In the upper atmosphere the main elements present are Oxygen and Nitrogen. Oxygen glows green and red, and Nitrogen glows blue and purple. This is why we were seeing so many amazing layers of colours through the sky. The different colours and intensities depend on the amount and the energy of the incoming particles.
Whilst we may not get another display like last week’s anytime soon, Scotland is not a bad place to be during the solar cycle peak, and with the Dark skies of Dumfries and Galloway there are some great odds for seeing the Dancing lights light up the sky over the next few years.
This guest blog and the graphics were submitted by Ishbel Carlyle who works at Kielder Observatory in Northumberland. Ishbel is also studying for a PhD in Auroral Physics at Northumberland University (16 May 2024)
Photos by Mike Bolam. See full Crawick Multiverse Aurora Gallery by Mike Bolam here.
Figure 3: Colours of Aurora
