Across the night sky, when conditions are right, a symphony of colour dances around. A cosmic wonder the Southern Lights, or Aurora Australis puts on a show of differing hues of red, green and purple.
While difficult to predict with certainty, recent advancement has given us a clearer understanding of the solar activity that powers this magnificent display.
🔬 The Mechanics of the Aurora Australis
The Process: Solar Wind to Light
These Aurora's are the result of a powerful interaction that begins with the Sun constantly emitting a flow of charged particles known as solar wind. When these particles encounter Earth’s magnetic field, they are channeled toward the poles. When upon entering the upper atmosphere, these high-energy particles excite atoms and molecules as these energised particles subsequently release their extra energy, it is emitted as tiny specks of light—producing the magnificent phenomenon we observe as the aurora.
Driving Aurora Intensity
The strength of the solar wind directly determines how active and visible the aurora will be. The most intense displays are caused by two primary events:
Coronal Mass Ejections (CMEs): These are massive explosions of plasma from the Sun. CMEs drive the strongest, brightest, and most active auroras.
Coronal Holes: These are areas where the Sun’s magnetic field allows a fast and steady stream of solar wind to escape. While generally producing less intense displays than CMEs, these high-speed streams are known to cause mild-to-moderately active auroras.
🎨 The Colour Code: How Altitude & Elements Define the Display
The most common colours are generated by Oxygen. A vivid green is created when oxygen is excited at altitudes generally between 100 and 200 kilometers. The less frequent, deep red colour appears higher in the atmosphere, typically above 200 kilometre's.
Nitrogen collisions also contribute significantly to the palette. Excited nitrogen gas often emits a glowing blue at mid-altitudes (100–200 km). Furthermore, nitrogen is responsible for the distinct reddish-purple or pink glow seen at the very lower edge of the aurora, below 100 kilometre's.
Since these reactions occur across multiple atmospheric layers simultaneously, the gases frequently mix, which is how the displays gain complexity, resulting in unique shades of purples, pinks, and occasional whites.
✨ Chasing the Aurora: Quick Guide
Chasing the Aurora: Quick Guide
Seeing and photographing the unpredictable Aurora Australis requires preparation and persistence, but produces great results when successful.
Viewing Essentials
Monitoring aurora forecast sites and community groups is the most reliable way to time your viewing. To maximise visibility, seek locations free of light pollution with a clear view of the southern horizon. The best opportunities typically arise, late at night, often between 10:00 PM and 2:00 AM local time.
Photography Checklist
Your smartphone can capture the aurora using its manual capabilities. By using a slower shutter speed, typically between 5 to 15 seconds this allows enough light in for your phone to capture the aurora. This needs to be used in combination with a higher ISO, increasing your cameras sensitivity to light. While a tripod will also help to stabilise your shot as well and is highly recommended.
Mastering these settings is key to capturing the display, though results will always depend on the aurora's intensity.