Photo opportunity #1
The Aurora Australis is not only the name of the ship that transported us here. It is also the name of the natural light display that is sometimes seen in the night sky. Auroras occur mostly in the polar regions and is visible almost every night at, or near, the Antarctic and Arctic Circles (66.5ºS and 66.5ºN).
The activity that creates an aurora starts at the sun. The super hot gases of the sun are made up of electrically charged particles called ions. The ions continuously stream from the sun as the solar wind. Most of the solar wind bypasses the Earth, deflected by the Earth’s magnetic field. Without this magnetic field the solar wind would blow away the fragile atmosphere, preventing life.
Some of the ions do however become trapped in a ring-shaped holding area around the planet, a region of the atmosphere called the ionosphere. In the ionosphere, the ions collide with gas atoms and the energy released causes a colorful, glowing light – an aurora.
The colour of the aurora is dependent on the gas. Oxygen emissions are green or brownish red depending on the amount of energy absorbed. Nitrogen emmisions give a blue or red; blue if the atom regains an electron after being ionized.
Auroras occur often at Macquarie Island, but as there are on average annually 315 days of rain, there is limited opportunities to witness them. We are always on the lookout when the sky clears.
The strength of an aurora has been found to be related to sunspot activity and a stronger solar wind. Last week we had a clear sky and a fairly strong aurora.
Barend (Barry) Becker
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