2003 Oct 31 Update
Where is the aurora visible? gives a good guide - if the colour is red or orange and the UK is near the edge of the coloured zone there is a good chance.
Today's Space Weather from the US Space Environment Centre is also useful. If the bar chart at the bottom of the graph is red, there is a good chance of auroral activity. This site includes The Latest Space Weather - the first two pages give current alerts and some diagrams of solar activity. Another diagram which gives some ideas as to the current location of the aurora is Auroral Activity Estimates.
NOAA have a Space Weather page with news stories and so do Space Science.
Solar Terrestrial Despatch have an Hourly auroral activity report which includes material from some of the above sites.
Here are a few pictures that I took from just outside
Cambridge of the major display of 2001 April 6/7:
04 Curtain and weak rays looking north
09 Strong red glow looking north east
13 Rays and red patches looking north west
19 Curtain and rays looking north west
09 Rayed curtain looking north
19 Brilliant red curtain with weak rays
25 Coronal activity at the zenith
There was another major display on 2001 July 15/16 however for Cambridge this was largely obliterated by moonlight and cloud.
I was lucky enough to see a minor display of the quiet auroral arc when cycling back to Cambridge from BAS on 2003 October 14, this lasted from around 17:30 to 18:00 UT. Visually the arc appeared white, a clearly different colour to clouds illuminated by street lights, whereas the image shows the arc as green.
A more impressive display occurred on 2003 October 29 following major flares and coronal mass ejections associated with two of the largest sunspot groups that have been seen for decades. Cambridge suffered from patchy cloud and light pollution, which tended to obscure the diffuse auroral glow that was the predominant form of the display, however at times there were bright rays reaching to at least 45° altitude. By contrast with the October 14 display, this display mostly showed up as red. A colleague living near Bury St Edmunds provided this nice image, showing the display from a darker location.
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