Aurora alert for tonight

February 18, 2011 | By | Add a Comment
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We MAY finally have the opportunity in Southern Australia (at least Southern Tasmania)  to see an aurora. These occur when gas erupted off the Sun in gigantic explosions impact the Earth’s magnetic field. The gas (or more strictly speaking charged particles) heat the Earth’s upper atmosphere sufficiently to cause it to glow. Aurora can take on a variety of forms – but the fainter ones appear as reddish or greenish moving clouds.

The ‘when’ to look is the problem. Aurora are unpredictable. The text book information states that the most likely time to look is around local midnight. That said, the only aurora I have seen was ( from the outskirts of Canberra in 2002) at around 8pm. The other problem is the Moon. The timing is pretty bad with the Full Moon occuring tonight. This means that the Moon will be a big bright unwanted light source in the sky and remain so almost all night. A final comment, aurora aren’t bright. If you live in a big city with lots of street lights, you will need to get in your car and drive away from the said lights.

Your location is also important. Observers in Southern Tasmania regularly see aurora when the Sun is active. I have seen one from Canberra and they have been seen from Brisbane when the Earth was hit by a cloud from a really big solar storm (only once from my research). A quick check of the Australian Government’s IPS Radio and Space Service’s website indicates that only Southern Tasmania may be likely to see an aurora tonight (assuming you have clear skies).

Finally, the cloud that is impacting the Earth’s magnetic field is only a prelude to the one that is expected to arrive tomorrow. That one was ejected from the Sun by a much larger ‘explosion’ (a Sun’s magnetic field line snapping) and hence will contain more gas. When it arrives, it has the potential to generate a larger aurora than tonights.

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