June: Evening sky colours Antarctica

Todor Iolovski quit his job as an electronics engineer for the adventure of a 14-month Antarctic posting as a Bureau of Meteorology Technical Officer (Engineering) at Australia’s Casey Station. In June 2008, on a clear, windless night at about midnight, Todor’s 30-year passion for photography enabled him to endure two hours outdoors at minus 20 degrees to take 10 long-exposure photographs. His picture of the Aurora australis was an exposure of 3 minutes 40 seconds, which also captured star trails as the earth turned. “In such very dry conditions, the camera won’t freeze,” Todor says, but he kept four spare batteries in his pocket because they can fail at such low temperatures. “The hard part was wandering around for new vantage points as the aurora changed direction, from east, to north-east, to south.” Todor only went inside when it got too cold to change the batteries.

Aurorae occur when streams of charged particles arriving from the sun travel along the earth’s magnetic field lines and collide with the upper atmosphere in a region known as the ionosphere. Also known as the Southern Lights, Aurora australis is most commonly observed over Antarctica but can also be seen further north — including Australia — during intense solar activity. The pictured aurora was at an altitude of 90 to 130 kilometres and emitted green light when the charged particles collided with atomic oxygen in the atmosphere. Other colours are emitted when charged particles collide with different gases. The phenomenon is named after Aurora, the Roman goddess of dawn. The stream of charged particles is sometimes called the solar wind.

Aurorae generally form within an arc a few hundred meters wide and hundreds to thousands of kilometres long. The arc typically is aligned east to west. Because of the potential impact aurorae have on communication systems — such as high frequency radio transmissions — the zones in which they form are predicted and monitored in the Southern hemisphere by the Bureau’s Ionospheric Prediction Service.

Note: The photograph in the printed calendar is NOT watermarked with a copyright symbol and name.

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