...the mysterious green flash just after sun disappears

Not the name of an obscure superhero but indeed a recognized phenomenon. I hate to sound like a broken record (how many young'uns out there have ever heard a broken record?!) but Scientific American did an article on that too, I would guess ten to twenty years ago. It even had a full-color picture of it on the cover!

Edit: And here's the latest Scientific American squib on the subject:
http://makeashorterlink.com/?T25E56923

Note the distortions of perceived time:
"(We also call interested readers' attention to "The Green Flash," by D. J. K. O'Connell, in Scientific American, January 1960, pp. 112-122.)"
"Ten or twenty years ago," he says...right!