The Aurora Australis appears over Tasmania, but what causes it?
The sun releases particles of plasma (which we call “solar wind”) through sunspots and coronal holes. They strike the earth’s magnetosphere at hundreds of km/s. Contained within the plasma are electrons. When these electrons collide with the gases in Earth’s upper atmosphere it ‘excites’ them into a higher energy state. When they move back down to their natural energy state, they emit a photon of light, which becomes the aurora. Collisions with oxygen produce green and yellow auroras while collisions with nitrogen produce pink, red, purple and blue auroras.
The sun goes through an 11 year cycle of solar maximum and solar minimum. During solar maximum there are more solar flares, resulting in a higher frequency of stronger auroras. Hobart, Tasmania, is at 42 degrees south latitude and typically experiences the Aurora Australis at least several times or more a year, dependent upon the solar cycle. Tasmania has also got some of the darkest skies in the world, especially when facing south of Hobart, so we are blessed to have fantastic views of the Southern Lights.
This panorama photograph of the Aurora Australis was taken from the top of Mt. Wellington / kunanyi, near the pinnacle.
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“…stop and consider God’s wonders.” (Job 37:14)
Whenever I go out to shoot aurora, I need the solar forecast to line up with the weather forecast, the work forecast and the babysitting forecast. Getting all of these factors to line up is far more of an improbability than the Southern Lights appearing here at 42 degrees south latitude. Thankfully they all came together on the night the Lord blessed me with this wonderful shot of the Aurora Australis from the summit of Kunanyi / Mt. Wellington.
Because this photo of the Aurora Australis was taken a couple days away from the summer solstice I needed to wait until nearly 11 pm for it to be dark enough to start capturing the aurora. A bushfire blanketed the horizon with a deep orange haze upon sunset. Even an hour later, the orange band was still visible to the camera, and it showed up in this shot. I really like it because it makes the the photograph look like a “night rainbow” to me. It artistically adds to the magnificent colour of the Aurora Australis, the spectacular southern sky and the sculpted rocks of the summit.