A new study of the magnetic space storms that create the northern and  southern lights could lead to a better understanding of natural  temperature variations in the polar regions. Surprisingly, large  temperature changes may be linked to auroral activity.

Reporting last week in the American Geophysical Union's Journal of  Geophysical Research, an international team of scientists from the UK  (British Antarctic Survey), Finland, USA, Switzerland, and New Zealand  (University of Otago) explain that large variations in surface temperatures across both poles occur during winters that experience a high  number of magnetic storms. The research sheds new light on the role that the Sun plays in controlling the Earth's climate and will lead to improved climate model predictions.

The northern and southern lights - the aurora - are created by energised particles from the Sun striking the Earth's atmosphere, releasing light. These particles also create chemicals (nitrogen oxides) high in the Earth's atmosphere that can destroy ozone during the long polar winter. In some winters there are lots of aurora, due to magnetic storms, but in other winters very few occur. The team found that the difference between the high and low auroral activity results in cooling and warming in surface temperature patterns of up to 4°C in the polar regions.

A climate modelling study had earlier predicted that energetic particles hitting the top of the atmosphere in polar regions may change temperatures by stimulating the production of nitrogen oxides. However, the conclusions of that study were not widely recognised, as they seemed somewhat unlikely. For the first time, experimental climate observations have confirmed this picture, with the large increases and decreases in polar temperatures being caused by changing magnetic storm levels, visible through the aurora.

Dr Craig Rodger of the University of Otago Physics Department said,

"The earlier climate modelling predicted this effect, but was not widely taken up by the scientific community. It looked slightly bit odd, maybe a bit too unlikely. The real surprise for us was to see the same pattern, with the same strength, in the experimental data. Suddenly it was clear that the Sun was changing the polar temperatures".

The research was lead by Dr Annika Seppälä of the British Antarctic Survey and the Finnish Meteorological who has recently been awarded a Marie Curie Fellowship by the European Union to work at BAS. The New Zeland connection comes from Dr Craig Rodger of the University of Otago. The other team members were Dr Mark Clilverd (British Antarctic Survey, UK), Dr Cora Randall (University of Colorado, USA) and Dr Eugene Rozanov (Physical-Meteorological Observatory/World Radiation Center, Switzerland). Dr Seppälä and her team now intends to investigate how the magnetic storms truly link to the polar surface temperatures, and show the exact role the northern lights play in these changes.

This study has been published as:

Geomagnetic activity and polar surface level air temperature variability by Annika Seppälä, Cora E. Randall, Mark A. Clilverd, Eugene Rozanov, and Craig J. Rodger is published in the October issue of the American Geophysical Union's Journal of Geophysical Research.

http://www.agu.org/journals/ja/

A preprint of the paper is available from:
http://www.physics.otago.ac.nz/space/2008JA014029-pip.pdf