Auroras in the winter night

What’s that amazing colour in the sky?

An aurora, also known as Aurora australis in the southern hemisphere and Aurora borealis in the northern hemisphere, is a natural light display in the Earth’s sky. It is most commonly seen in the higher latitude regions, close to the Arctic and Antarctic.

What causes an aurora starts 150 million kilometres away with the Sun. The sun works as a thermonuclear reactor, turning hydrogen atoms into helium atoms, producing million-degree temperatures and powerful magnetic fields. In some places, strong magnetic fields push their way to the Sun’s surface, then eject outwards into space carrying hot gases and charged particles, also known as plasma. Known as solar wind, or sometimes as a coronal mass ejection (CME), these charged particles (electrons and protons) travel towards Earth at an incredible speed of up to 1584000km/h or 440km/second.

Just like the Sun, the Earth produces its own magnetic field. Our magnetosphere shields us from most of the Sun’s particles by deflecting them but some travel along Earth’s magnetic field lines and are funnelled into the Earth’s atmosphere at the poles, where the magnetosphere is weaker. When this happens, the electrons in the solar wind collide with oxygen and nitrogen atoms in the Earth’s atmosphere. These collisions, usually taking place between 60 to 300km above ground, cause the oxygen and nitrogen to become excited. When this happens, energy is released in the form of particles of light, known as photons.

This glow is known as the aurora. The colour of an aurora depends on which gas the electrons and protons collide with and the amount of energy that is being transferred. The quicker the collision, the more photons released and hence the brighter the colour. Green (at lower altitudes) or red (at higher altitudes) in the sky indicates oxygen molecules are being hit whereas nitrogen molecules emit a blue/violet light. The appearance of the aurora is defined by the changing flow of charged particles and the varying magnetic fields. They are often described as sheets or curtains.

On station, those interested in viewing auroras can subscribe to an aurora alert hotline. When someone sees an aurora, they dial a number which in turn calls everyone on station that has subscribed to the hotline.


Getting to know a Casey expeditioner — Tanya Maddison

Name: Tanya Maddison

Nicknames: Tan, T. San, Tanya San

From: Newcastle

Previous seasons: N/A

Job title: Weather Observer

Describe your role in two sentences: I perform synoptic weather observations, release and monitor weather balloons, conduct air sampling for CSIRO, administration and basic maintenance of instruments. In summer, aviation weather reports were conducted to meet requirements of the summer flying program.

What did you do before you joined the AAD?  I worked as a stewardess on Australia’s icebreaker, Aurora Australis and prior to that, I was a teacher.

What is your favourite part of your job here at Casey? The variety.  Apart from my primary job, this unique work environment affords other opportunities to learn skills in different areas.  For example, I have learned about hydroponics (a volunteer job on station) and firefighting to name a couple.

If you were not a weather observer what would be your dream job? Something that took me to different places around the globe, being immersed in different cultures and environments. 

How does this season at Casey compare to your previous seasons down south? N/A

What do you like to do in your spare time?  I like to get outside and explore this place.  I cross-country ski, get to the gym, tinker on the guitar, spend time in hydroponics tending to the plants and some amateur photography. I’m aspiring to get a good aurora shot!

What song sums up your Casey experience so far? Wish You Were Here by Pink Floyd. I am learning it on guitar.

What actor would play you in a film version of our 72nd ANARE season here at Casey? I don’t watch too many films so it’s difficult to choose a character.  I’d prefer to be a musician, guitarist, with 10 000 practising hours under my belt so that I could rock out any song I wished with minimal fuss. 

Favourite piece of Australian Antarctic Division kit?  Both the issued mittens and balaclava are getting a good run for extended outdoor activities now that winter is upon us. 

What is your favourite book / movie (or both) and why? 

Movie: Probably The Castle.  It’s quintessentially Australian and lots of the minor details happening with props in the background that make me laugh.

Book:  I don’t read a lot. I think the last book I read was Return in the Wake by Cathy Hawkins. I met her on the Aurora Australis.  It’s a book about her intrepid sailing adventures. After chatting to her about her experiences and with an interest in sailing, I found it inspirational.

What is your typical ‘Slushy FM’ genre? Do you have a particular favourite? My taste in music is universal but it depends on my mood.  I quite like listening to jazz, or chillout background music like Morcheeba or Angus and Julia Stone. Anything except techno and extreme heavy metal!

Describe your Casey experience with: a sight, a smell, a sound, a feeling and a taste.

Sight: The sky at night away from the lights on station on a clear night.

Smell: The earthiness of the seedlings and tomato plants in hydroponics.

Sound: The chalky crunch under foot when walking on the dry, cold snow.

Feeling: Chilly outside!

Taste: Hydroponic tomatoes and herbs.

Do you have a favourite quote that you’d like to leave us with?

“Success is not final, failure is not fatal: it is the courage to continue that counts.” (Winston Churchill)

Something thing people may not know about you:  I can speak French.