There was a moderate storm that hit the earth's magnetic field on March 17th causing some nice aurora. You can check the latest space weather report here http://spaceweather.com

In fact, by keeping an eye on space weather (for example at the link that Dawn posted), you'll be able to tell when storms like that are going to happen. Solar storms happen when high-energy charged particle flung out by the Sun hit the Earth and interact with its magnetic field. These storms come from explosions on the Sun and usually take a day or two before reaching the Earth. Though we don't currently have a way to predict when the explosions (solar flares and solar mass ejections) will happen, once they do we can often tell if the particles are flung out in the direction of the Earth and will cause an electromagnetic storm.

And check out these beautiful movies made using data from the Solar Dynamics Observatory of the solar storm: http://www.facebook.com/p...?v=10151560294871869 Some beautiful aurora photos can be seen on that facebook page too. Claire

We were also lucky to see some auroras in Helsinki! I live in Finland and in northern parts of our country auroras are very frequent (below is an aurora photo that my friend who lives ín Oulu took during that storm). But t is only a few times per year you can see them in Helsinki and often it is too cloudy or too much light. According to so-called Dst index that measures the intensity of an electric current that circles the Earth the minimum was -132 nT. When Dst is below -100 nT the storm in the Earth's magnetosphere is usually called intense. At solar maximum intense magnetic storms are not uncommon. During the maximum year (year 2000) of the previous solar cycle 23 there were more than ten intense storms. But this current solar maximum has been so far quite weak..

Emilia