Earlier quoted context omitted.
Exactly the same trigger here. I had one just the other day at the pub. Sitting outside, under shade, but to my left was a bright spot. It’s weird how I can sense it arriving ... something about the quality of my vision subtly changes, and there it is. Fortunately for me it isn’t accompanied by a headache. It’s just really unsettling. At least now I’ve learned to recognise them and I just try to chill out while it do…
For whatever it’s worth, too much caffeine and dehydration does this to me. Chugging about 48 oz of water and throwing on a face mask for 30-60 minutes usually clears it up. If I do “nothing” it takes significantly longer to clear up.
The aura (with scintillating scotoma) starts coming on usually an hour or so after the exercise is done, and I know I've got about 15-20 minutes before the actual migraine hits. Got prescribed Sumatriptan and it maybe reduced the intensity by about 25%. I'll have to try the water chugging, maybe with rehydration salts to speed up absorption.