31 August, 2009 Halley
During the winter months on the Antarctic continent not only do we experience 24 hour darkness but we are privileged to see the aurora australis. Here at Halley Station we were looking forward to experiencing many a night gazing at the dancing lights as they flitter across the sky. Reading the small print however, revealed that there is a cycle of activity that revolves around an 11 year period. It seems that 2009 is a low solar activity year and hence our expectations might have been a bit high.
Large flares or solar explosions from the sun will expel numerous amounts of solar particles which make their way towards Earth. These particles come into contact with the Earth’s magnetosphere and are directed towards the polar regions. High energy particles then cascade into the highest parts of the Earth’s atmosphere, ionising gases. It’s this process that emits the glows that we see on Earth. The variation of colour is a result of particles with different energies ionising different gases.
So we wait patiently every night checking our aurora prediction chart for high numbers. The nightwatch person is given the task to carry out the night-time meteorology observations and keep a keen eye on the skies for hints of an aurora. Not an easy task if you have never seen one before! Luckily, as I was here last year I was able to tell everyone that it often looks just like a cloud but then moves in a strange fashion. There has been many a night when we should have seen an aurora but other factors limited us. Compete cloud cover, snow and blowing snow will reduce our ability on the ground to see anything from the ground.
Finally, at 3am on a Monday morning the whole station is woken up with the nightwatchman running up and down the corridor shouting ‘Aurora!’. Bleary eyed we dress up warm and venture outside. We are rewarded with an aurora to the southeast of the station. The air is filled with excited chatter, oohs and ahhs as we gaze up at the sky. To us we don’t see much of the colours of the aurora but instead it appears as dancing clouds high in the atmosphere. Cameras are dragged about and folk are trying to remember how to set exposures and apertures to catch this elusive display. Camera lenses are able to capture the colours and a couple of successful photos were taken. Within an hour it had died down considerably. Cold but happy we made our way inside to warm up and go back to bed.
Hope is not lost though. Days later, another 3am call is heard and this time, more prepared for the cold, with batteries charged and cameras ready, some dedicated gazers head out to see the sight. This time the whole sky appears to be covered. Though still not as green as we expected the display is nonetheless impressive.
Everywhere we look the aurora ebbs and flows. Sometimes it swirls in a big mass or ribbons stretch across the sky in waves. By 5am this particular one was still going strong but our ability to stay outside together with frozen cameras led most back indoors. To our surprise it was still going at 9am that morning.
We know that many other regions in the Antarctic have received impressive displays this year but we are happy with the opportunity to have at least seen a couple here at Halley.
Winter Base Commander
Halley Research Station