Blog Archive


Search This Blog

Saturday, October 29, 2005

Aurora Blogging....again

I thought that I might inflict a few more of my pictures on you. On the night of the 8th of October we actually had some clear skies in amongst all the rain. In addition we had a couple of substorms kick off as well, leading to some fantastic auroral displays that went on and on and on. A red arc was reported but due to work commitments I failed to see it, let alone get a photo of it. However there was a cracking arc, almost overhead. You can see some ray structure pointing down the field line towards us at the bottom left corner of the picture. The magnetic field at the radar site is inclined at 12 degrees to the south.

A little later there was a fantastic curled arc that held a special treat. You can see that this one had a nice reddy edge to the bottom of it. This indicates that there were more energetic particles present. The green light that you see comes from emission that is primarily in the ionosphere at ~120 km altitude. The red border is below that. The more traditional red emission that is seen at lower latitudes is from softer (less energetic) particles in the higher ionosphere.

In addition I managed to take advantage of the very bright emission to catch some good ray structure. One problem with photographing the aurora with a standard quality camera is that you cannot get the detail you might like on short timescales. As I might have said before, the aurora is often exceptionally dynamic with small scale changes rapidly fluctuating across the arcs and waves shooting from horizon to horizon. When you are limited to 10-15 second exposures it is too easy to miss all this. This picture shows that the rays in the arc taken at 5 second exposure.

And if you are sick of the aurora pictures then I offer this one. Taken in the fading light of the evening it shows Mars sitting bright in the sky alongside the radar dish. The ambient light looks brighter than it was since I used a 10-second exposure. This was taken looking north and if you look closely you can see a faint auroral arc in the background, below Mars and to the right of the dish. I resisted the urge to enhance it.

No comments: