The Great Aurora of May 2024

When was it?

The peak of the Great Aurora of 2024 occurred around the 10th,  11th and 12th of May 2024 depending on where you were . Aurora, or lights in the parts of the Earth’s atmosphere which are usually only seen in regions closer to the north and south pole, were seen in much of southern Australia and across New Zealand, with some reports of Aurora being seen even in Queensland!

What causes Aurora?

The frequency and size of sunspots seen on the surface of our nearest star – the Sun – change over an approx. 11 year period. We’re heading in the period of peak  activity called  Solar Maximum. Sunspots appear like as darker regions compared to the rest of the Sun’s disk but are in fact areas of intense storms of magnetically charged plasma particles. (This is a very simplified explanation of the complex changes seen on the Sun’s surface. On any clear day, pop into BINTEL and we’ll show you the Sun through a dedicated Solar Telescope and explain more.)

Sunspots can  produce loops of plasma that crash back onto the Sun’s surface,  send out ultraviolet light and x-rays that can play havoc with satellites and communication.  Such radiation travels at the speed of light and impacts the Earth only a few minutes after it’s emitted from the Sun.

The Earth is surrounded by a  series of our own magnetic fields which are called the magnetosphere. This protects us from harmful radiation from the Sun as well as from other sources further out into space.

The Sun can also eject charge particles during these storms. These are streams of material, not different wavelengths of “light” like high energy ultraviolet or x-rays and travel far more slowly.  They take some hours or days to reach the Earth and if aimed just right and interact with the magnetosphere, will cause the Aurora.  This stream of particles is called a Coronal Mass Ejection or CME.  If lined up towards Earth, particles in a CME from the Sun will strike the magnetosphere and be directed into the upper regions of the Earth’s atmosphere. The atoms in the atmosphere are “excited” by these particles from the Sun slamming into them and release energy as photons or light as we see it.

What did we see? Why all the different colours?

The different colours seen in Aurora are the due to different gasses in our atmosphere, much like the different colours seen in old school neon lights.   You’ll be able to see a all these different colours in our customer photos below.)

Green – the most common colour seen in Aurora as our eyes are sensitive to this part of the spectrum.  This happens when CME particles interact with oxygen at around 100 to 300kms altitude

Red – interactions with oxygen at higher altitude, from  300 to 400kms

Pink/red – this produced by nitrogen at approx 100km.

Blue or purple – particles hitting helium and hydrogen right on the edge of the Earth’s atmosphere as these gases are the lightest and float above other elements of the atmosphere. The colours are hard to see against a dark sky background, however there’s some images below showing them.

Does a CME needs to be a direct hit to cause an Aurora?

Yes.  Many of the Solar storms we see emit CMEs in all different directions. We won’t see the particles as they travel through the Solar System unless they interact with something in their path.

Why was this such as massive display of Aurora?

Solar storms are measured by various scales. Think of these as similar to cyclones or earthquake measurements.  One common scale is the G Scale. The most severe of these G5 – are rare events.

The Great Aurora of 2024 was produce by a G5 geomagnetic storm The last time a G5 even occurred was in 2003. (As I’m writing this, we’re  at G0 geomagnetic conditions with a slight change a  G1)

From the 7th to the 11th of May at least seven CMEs headed towards Earth including from the sunspot group AR3664 pictured below taken by Franco Fantasia & Guiseppe Conzo.

Aren’t Aurora normally only seen much closer to the Earth’s polar regions?

Yes! Due to the shape of the Earth’s magnetic field lines, nearly all of the charged particles from the Sun’s CME are directed into the atmosphere near the North and South poles. In the case of this event, the intensity of the CME was so massive that Aurora was visible at latitudes that have never seen them in living memory.

Will it happen again?  How big was this event?

There’s no doubt this was a rare event! We’re unable to predict exactly when aurora will occur in the future with any certainty but we can get a heads up on likely aurora based on our observations of the Sun.  As mentioned, the surface of the Sun is becoming more active during Solar maximum and more frequent and strong aurora are expected.

The events of a few weeks are quite rare and it compares with major aurora events in past decades.

Some commentators are suggesting that the aurora seen recently were more widespread and widely seen than any aurora of the last 500 years! It’s the only G5 event since the availability of smartphone (the last one being in 2003) and there’s a strong possibility of there being more photos of the Great Aurora of 2024 than all other auroras put together.

How I keep an eye on aurora events and get involved?

One citizen science project is Aurorasaurus located here.  This projects tracks aurora in real-time based on local reports and send you updates.  It helps scientists to build valuable data on aurora to build into space weather models and theories.

The Australian Space Weather Alert System located here will you updated with current Solar conditions, news and expected events.

The US government’s Space Weather Prediction Center located here is also a key resource.

Cheers,

Earl White

BINTEL

22nd May 2024