Can't afford that winter trip to Iceland or Alaska? No worries, you can make a lovely little aurora at home.
Here's my recipe.
(1) Film developer, fairly strong e.g. 1+0 or 1+1. I'm using wd2d+ (10 mL part A, 10 mL part B + 500 mL water);
(2) Stop bath, e.g. ilfostop, at 1+4 or so.
In your darkroom, after your eyes have adjusted, pour some some (2) into (1). Oooh... :o
Now, this is an effect that I saw very weakly a few times before whilst tray developing, but convinced myself that I was hallucinating. But today I decided to do an experiment. After noticing a few faint flashes (quarter second or so in duration) when putting freshly developed film into the stop bath, I thought at first that this must be something to do with the film, but then I splashed some stop bath into the developer bath and... nice big flash. So of course I slowly poured the two baths together in the dark and confirmed that you get a nice glowing, chemiluminescent bath.
This latest observation of aurora stopealis was with wd2d+ developer and ilfostop. I dont know whether it will work with other developers- try and see for yourself! I may have seen it faintly before with other developers, but with the wd2d+ and ilfostop, the effect seems quite pronounced.
P.S. The stop flash has no apparent ill effect on the film. Normally you may not see it, because you may be inclined to shake extra developer off the film before dunking it into stop bath... or you may simply use a warm water bath to stop.
P.P.S. Explanations, anyone? Points will be awarded for the most exotic explanation.