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.
In addition to chugging water and staying in the dark with a face mask, I've found that taking raw honey right as it's coming on makes it go away rapidly.
My long term prevention is taking magnesium daily and LSD once or so a year. Once I started doing that the frequency went to almost zero, and whenever I don't do that they start up again.